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000
FXUS63 KLOT 251602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS STILL POSSIBLE THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

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000
FXUS63 KLOT 251602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS STILL POSSIBLE THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

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000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251302
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
802 AM CDT MON MAY 25 2015

.UPDATE...
756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

KMD

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 251302
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
802 AM CDT MON MAY 25 2015

.UPDATE...
756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

KMD

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 251139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUEING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUEING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250810
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUEING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 250810
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUEING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250740
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250740
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 250556
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1256 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 250556
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1256 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250556
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1256 AM CDT MON MAY 25 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 250323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
722 PM CDT

CONTINUE TO MONITOR WHAT AT PRESENT ARE WIDELY SCATTERED STORMS
ACROSS NORTH CENTRAL AND NORTHEAST ILLINOIS. ANALYSIS OF
OBSERVATIONS INDICATE THE SURFACE WARM FRONT DRAPED FROM NEAR
CLINTON IA TO ROCHELLE TO NEAR JOLIET AND LANSING. THE CURRENT
TORNADO WATCH AREA OVERLAPS THE BETTER DEEP AND LOW-LEVEL SHEAR
FOR STORM UPDRAFT PERSISTENCE...ALONG THIS DEW POINTS APPEARED
POOLED OF 65 TO 70...AIDING IN LOW-LEVEL CAPE THAT SHOULD ENABLE
SURFACE-BASED POTENTIAL FOR AT LEAST A COUPLE HOURS AFTER DARK.
THIS IS VERIFIED BY SOUTHERLY WINDS ACROSS CENTRAL ILLINOIS INTO
THE SOUTHERN CWA STILL GUSTING AT 25-30 KTS AS OF 715 PM.
HOWEVER...UNCERTAINTY EXISTS ON HOW WIDESPREAD COVERAGE OF STORMS
WILL BE...ESPECIALLY WITH SOMEWHAT OF A DOWNTICK THE PAST 30-45
MINUTES. HIGH-RESOLUTION GUIDANCE SHOWS SPREAD IN
SOLUTIONS...ALTHOUGH AN AGREEMENT THAT EAST OF ILLINOIS HIGHWAY 47
/MUCH OF THE CHICAGO METRO/...THAT COVERAGE WILL BE VERY LIMITED
TO NONE THROUGH THIS EVE. RECENT RADAR AND SATELLITE TRENDS WOULD
TEND TO SUPPORT THIS...SO THE ATTENTION CONTINUES TO BE ON NORTH
CENTRAL ILLINOIS.

A FEW STORMS HAVE EXHIBITED ROTATION...INCLUDING ONE IN THE DVN
CWA THAT DID PRODUCE A TORNADO NEAR ELIZA PER LOCAL STORM REPORT.
EARLIER A STORM THAT TRACKED FROM LEE COUNTY INTO OGLE COUNTY FROM
610 TO 650 PM EXHIBITED ROTATION AS IT NEARED AND OVERTOPPED THE
BOUNDARY. THIS VERIFIES THE NORTHERN END OF THE WARM SECTOR TO THE
BOUNDARY BEING A HELICITY RICH ENVIRONMENT. AS LONG AS STORMS CAN
TRACK ALONG IT /I.E. CONDITIONAL THREAT/...AND THE BOUNDARY LAYER
CAN REMAIN MIXED WITH PARCELS LIFTING FROM THE SURFACE OR NEAR
IT...THEN A BRIEF TORNADO THREAT WILL CONTINUE THIS EVENING.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...MORE SLOWLY THAN EXPECTED...TURNING SOUTH AND
  INCREASING.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING AND EARLY AFTERNOON.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM TO LOW CONFIDENCE ON WIND TRENDS OVERNIGHT BUT HIGH
  TOMORROW.

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
722 PM CDT

CONTINUE TO MONITOR WHAT AT PRESENT ARE WIDELY SCATTERED STORMS
ACROSS NORTH CENTRAL AND NORTHEAST ILLINOIS. ANALYSIS OF
OBSERVATIONS INDICATE THE SURFACE WARM FRONT DRAPED FROM NEAR
CLINTON IA TO ROCHELLE TO NEAR JOLIET AND LANSING. THE CURRENT
TORNADO WATCH AREA OVERLAPS THE BETTER DEEP AND LOW-LEVEL SHEAR
FOR STORM UPDRAFT PERSISTENCE...ALONG THIS DEW POINTS APPEARED
POOLED OF 65 TO 70...AIDING IN LOW-LEVEL CAPE THAT SHOULD ENABLE
SURFACE-BASED POTENTIAL FOR AT LEAST A COUPLE HOURS AFTER DARK.
THIS IS VERIFIED BY SOUTHERLY WINDS ACROSS CENTRAL ILLINOIS INTO
THE SOUTHERN CWA STILL GUSTING AT 25-30 KTS AS OF 715 PM.
HOWEVER...UNCERTAINTY EXISTS ON HOW WIDESPREAD COVERAGE OF STORMS
WILL BE...ESPECIALLY WITH SOMEWHAT OF A DOWNTICK THE PAST 30-45
MINUTES. HIGH-RESOLUTION GUIDANCE SHOWS SPREAD IN
SOLUTIONS...ALTHOUGH AN AGREEMENT THAT EAST OF ILLINOIS HIGHWAY 47
/MUCH OF THE CHICAGO METRO/...THAT COVERAGE WILL BE VERY LIMITED
TO NONE THROUGH THIS EVE. RECENT RADAR AND SATELLITE TRENDS WOULD
TEND TO SUPPORT THIS...SO THE ATTENTION CONTINUES TO BE ON NORTH
CENTRAL ILLINOIS.

A FEW STORMS HAVE EXHIBITED ROTATION...INCLUDING ONE IN THE DVN
CWA THAT DID PRODUCE A TORNADO NEAR ELIZA PER LOCAL STORM REPORT.
EARLIER A STORM THAT TRACKED FROM LEE COUNTY INTO OGLE COUNTY FROM
610 TO 650 PM EXHIBITED ROTATION AS IT NEARED AND OVERTOPPED THE
BOUNDARY. THIS VERIFIES THE NORTHERN END OF THE WARM SECTOR TO THE
BOUNDARY BEING A HELICITY RICH ENVIRONMENT. AS LONG AS STORMS CAN
TRACK ALONG IT /I.E. CONDITIONAL THREAT/...AND THE BOUNDARY LAYER
CAN REMAIN MIXED WITH PARCELS LIFTING FROM THE SURFACE OR NEAR
IT...THEN A BRIEF TORNADO THREAT WILL CONTINUE THIS EVENING.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...MORE SLOWLY THAN EXPECTED...TURNING SOUTH AND
  INCREASING.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING AND EARLY AFTERNOON.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM TO LOW CONFIDENCE ON WIND TRENDS OVERNIGHT BUT HIGH
  TOMORROW.

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 250033 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
733 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
722 PM CDT

CONTINUE TO MONITOR WHAT AT PRESENT ARE WIDELY SCATTERED STORMS
ACROSS NORTH CENTRAL AND NORTHEAST ILLINOIS. ANALYSIS OF
OBSERVATIONS INDICATE THE SURFACE WARM FRONT DRAPED FROM NEAR
CLINTON IA TO ROCHELLE TO NEAR JOLIET AND LANSING. THE CURRENT
TORNADO WATCH AREA OVERLAPS THE BETTER DEEP AND LOW-LEVEL SHEAR
FOR STORM UPDRAFT PERSISTENCE...ALONG THIS DEW POINTS APPEARED
POOLED OF 65 TO 70...AIDING IN LOW-LEVEL CAPE THAT SHOULD ENABLE
SURFACE-BASED POTENTIAL FOR AT LEAST A COUPLE HOURS AFTER DARK.
THIS IS VERIFIED BY SOUTHERLY WINDS ACROSS CENTRAL ILLINOIS INTO
THE SOUTHERN CWA STILL GUSTING AT 25-30 KTS AS OF 715 PM.
HOWEVER...UNCERTAINTY EXISTS ON HOW WIDESPREAD COVERAGE OF STORMS
WILL BE...ESPECIALLY WITH SOMEWHAT OF A DOWNTICK THE PAST 30-45
MINUTES. HIGH-RESOLUTION GUIDANCE SHOWS SPREAD IN
SOLUTIONS...ALTHOUGH AN AGREEMENT THAT EAST OF ILLINOIS HIGHWAY 47
/MUCH OF THE CHICAGO METRO/...THAT COVERAGE WILL BE VERY LIMITED
TO NONE THROUGH THIS EVE. RECENT RADAR AND SATELLITE TRENDS WOULD
TEND TO SUPPORT THIS...SO THE ATTENTION CONTINUES TO BE ON NORTH
CENTRAL ILLINOIS.

A FEW STORMS HAVE EXHIBITED ROTATION...INCLUDING ONE IN THE DVN
CWA THAT DID PRODUCE A TORNADO NEAR ELIZA PER LOCAL STORM REPORT.
EARLIER A STORM THAT TRACKED FROM LEE COUNTY INTO OGLE COUNTY FROM
610 TO 650 PM EXHIBITED ROTATION AS IT NEARED AND OVERTOPPED THE
BOUNDARY. THIS VERIFIES THE NORTHERN END OF THE WARM SECTOR TO THE
BOUNDARY BEING A HELICITY RICH ENVIRONMENT. AS LONG AS STORMS CAN
TRACK ALONG IT /I.E. CONDITIONAL THREAT/...AND THE BOUNDARY LAYER
CAN REMAIN MIXED WITH PARCELS LIFTING FROM THE SURFACE OR NEAR
IT...THEN A BRIEF TORNADO THREAT WILL CONTINUE THIS EVENING.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SHRA AND TSRA CHANCES THIS EVENING...ESPECIALLY WEST OF ORD/MDW.

* WINDS SHIFTING FROM EAST TO SOUTH THIS EVENING.

* ADDITIONAL SHRA/TSRA CHANCES OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS TOMORROW.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS THIS EVENING AND
  OVERNIGHT.

* MEDIUM CONFIDENCE ON TIMING OF WIND SHIFT...BUT HIGH CONFIDENCE
  THAT WINDS GO SOUTH THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE IN WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 250033 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
733 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
722 PM CDT

CONTINUE TO MONITOR WHAT AT PRESENT ARE WIDELY SCATTERED STORMS
ACROSS NORTH CENTRAL AND NORTHEAST ILLINOIS. ANALYSIS OF
OBSERVATIONS INDICATE THE SURFACE WARM FRONT DRAPED FROM NEAR
CLINTON IA TO ROCHELLE TO NEAR JOLIET AND LANSING. THE CURRENT
TORNADO WATCH AREA OVERLAPS THE BETTER DEEP AND LOW-LEVEL SHEAR
FOR STORM UPDRAFT PERSISTENCE...ALONG THIS DEW POINTS APPEARED
POOLED OF 65 TO 70...AIDING IN LOW-LEVEL CAPE THAT SHOULD ENABLE
SURFACE-BASED POTENTIAL FOR AT LEAST A COUPLE HOURS AFTER DARK.
THIS IS VERIFIED BY SOUTHERLY WINDS ACROSS CENTRAL ILLINOIS INTO
THE SOUTHERN CWA STILL GUSTING AT 25-30 KTS AS OF 715 PM.
HOWEVER...UNCERTAINTY EXISTS ON HOW WIDESPREAD COVERAGE OF STORMS
WILL BE...ESPECIALLY WITH SOMEWHAT OF A DOWNTICK THE PAST 30-45
MINUTES. HIGH-RESOLUTION GUIDANCE SHOWS SPREAD IN
SOLUTIONS...ALTHOUGH AN AGREEMENT THAT EAST OF ILLINOIS HIGHWAY 47
/MUCH OF THE CHICAGO METRO/...THAT COVERAGE WILL BE VERY LIMITED
TO NONE THROUGH THIS EVE. RECENT RADAR AND SATELLITE TRENDS WOULD
TEND TO SUPPORT THIS...SO THE ATTENTION CONTINUES TO BE ON NORTH
CENTRAL ILLINOIS.

A FEW STORMS HAVE EXHIBITED ROTATION...INCLUDING ONE IN THE DVN
CWA THAT DID PRODUCE A TORNADO NEAR ELIZA PER LOCAL STORM REPORT.
EARLIER A STORM THAT TRACKED FROM LEE COUNTY INTO OGLE COUNTY FROM
610 TO 650 PM EXHIBITED ROTATION AS IT NEARED AND OVERTOPPED THE
BOUNDARY. THIS VERIFIES THE NORTHERN END OF THE WARM SECTOR TO THE
BOUNDARY BEING A HELICITY RICH ENVIRONMENT. AS LONG AS STORMS CAN
TRACK ALONG IT /I.E. CONDITIONAL THREAT/...AND THE BOUNDARY LAYER
CAN REMAIN MIXED WITH PARCELS LIFTING FROM THE SURFACE OR NEAR
IT...THEN A BRIEF TORNADO THREAT WILL CONTINUE THIS EVENING.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SHRA AND TSRA CHANCES THIS EVENING...ESPECIALLY WEST OF ORD/MDW.

* WINDS SHIFTING FROM EAST TO SOUTH THIS EVENING.

* ADDITIONAL SHRA/TSRA CHANCES OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS TOMORROW.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS THIS EVENING AND
  OVERNIGHT.

* MEDIUM CONFIDENCE ON TIMING OF WIND SHIFT...BUT HIGH CONFIDENCE
  THAT WINDS GO SOUTH THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE IN WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SHRA AND TSRA CHANCES THIS EVENING...ESPECIALLY WEST OF ORD/MDW.

* WINDS SHIFTING FROM EAST TO SOUTH THIS EVENING.

* ADDITIONAL SHRA/TSRA CHANCES OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS TOMORROW.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS THIS EVENING AND
  OVERNIGHT.

* MEDIUM CONFIDENCE ON TIMING OF WIND SHIFT...BUT HIGH CONFIDENCE
  THAT WINDS GO SOUTH THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE IN WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 242349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SHRA AND TSRA CHANCES THIS EVENING...ESPECIALLY WEST OF ORD/MDW.

* WINDS SHIFTING FROM EAST TO SOUTH THIS EVENING.

* ADDITIONAL SHRA/TSRA CHANCES OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS TOMORROW.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS THIS EVENING AND
  OVERNIGHT.

* MEDIUM CONFIDENCE ON TIMING OF WIND SHIFT...BUT HIGH CONFIDENCE
  THAT WINDS GO SOUTH THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE IN WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SHRA AND TSRA CHANCES THIS EVENING...ESPECIALLY WEST OF ORD/MDW.

* WINDS SHIFTING FROM EAST TO SOUTH THIS EVENING.

* ADDITIONAL SHRA/TSRA CHANCES OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS TOMORROW.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS THIS EVENING AND
  OVERNIGHT.

* MEDIUM CONFIDENCE ON TIMING OF WIND SHIFT...BUT HIGH CONFIDENCE
  THAT WINDS GO SOUTH THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE IN WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 242349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SHRA AND TSRA CHANCES THIS EVENING...ESPECIALLY WEST OF ORD/MDW.

* WINDS SHIFTING FROM EAST TO SOUTH THIS EVENING.

* ADDITIONAL SHRA/TSRA CHANCES OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS TOMORROW.

LENNING

//DISCUSSION...UPDATED 00Z...

TIMING IS UNCERTAIN...BUT A WARM FRONT LIFTING NORTH THROUGH THE
AREA THIS EVENING WILL TURN WINDS FROM EAST TO SOUTHEAST AND
EVENTUALLY TO SOUTH. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN POSSIBLE AT THE TERMINALS THIS EVENING...BUT MORE
FAVORABLE AREA IS TO THE WEST. WITH SOUTHERLY WINDS BRINGING
INCREASED MOISTURE OVERNIGHT...ADDITIONAL SHRA/TSRA IS EXPECTED
TO DEVELOP LATE. BY MORNING THESE SOUTHERLY WINDS STRENGTHEN
CONSIDERABLY AND BECOME QUITE GUSTY AS WELL.

LENNING

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE ON CONVECTIVE TRENDS THIS EVENING AND
  OVERNIGHT.

* MEDIUM CONFIDENCE ON TIMING OF WIND SHIFT...BUT HIGH CONFIDENCE
  THAT WINDS GO SOUTH THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE IN WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242241 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
541 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SHRA AND POSSIBLE TSRA THIS EVENING...AND SHRA AGAIN TONIGHT.

* WARM FRONT LIFTING THROUGH...SHIFTING WINDS FROM EAST TO SOUTH.

* STRONG AND GUSTY SOUTH WINDS TOMORROW MORNING.

LENNING

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM TO HIGH CONFIDENCE ON SHRA/TSRA TRENDS.

* MEDIUM CONFIDENCE REGARDING TIMING OF WIND SHIFT THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE OF STRONG AND GUSTY WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 242241 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
541 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SHRA AND POSSIBLE TSRA THIS EVENING...AND SHRA AGAIN TONIGHT.

* WARM FRONT LIFTING THROUGH...SHIFTING WINDS FROM EAST TO SOUTH.

* STRONG AND GUSTY SOUTH WINDS TOMORROW MORNING.

LENNING

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM TO HIGH CONFIDENCE ON SHRA/TSRA TRENDS.

* MEDIUM CONFIDENCE REGARDING TIMING OF WIND SHIFT THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE OF STRONG AND GUSTY WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242241 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
541 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SHRA AND POSSIBLE TSRA THIS EVENING...AND SHRA AGAIN TONIGHT.

* WARM FRONT LIFTING THROUGH...SHIFTING WINDS FROM EAST TO SOUTH.

* STRONG AND GUSTY SOUTH WINDS TOMORROW MORNING.

LENNING

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM TO HIGH CONFIDENCE ON SHRA/TSRA TRENDS.

* MEDIUM CONFIDENCE REGARDING TIMING OF WIND SHIFT THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE OF STRONG AND GUSTY WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

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000
FXUS63 KLOT 242241 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
541 PM CDT SUN MAY 24 2015

.MESOSCALE DISCUSSION...
540 PM CDT

THE STORM PREDICTION CENTER HAS COLLABORATED A TORNADO WATCH
THAT INCLUDES PART OF NORTH CENTRAL ILLINOIS. THIS IS FOR MAINLY
BRIEF TORNADO POTENTIAL...PARTICULARLY NEAR A WARM FRONTAL
BOUNDARY.

THE WARM FRONT HAS TRANSLATED NORTHWARD THROUGH THE MID
TO LATE AFTERNOON...WITH DEW POINTS IN THE MID 60S TO EVEN SOME
UPPER 60S HAVING SURGED NORTHWARD TO THE BOUNDARY. THIS BOUNDARY
IS PRESENTLY LOCATED FROM THE NORTH SIDE OF THE QUAD CITIES TO
JUST NORTH OF STERLING THROUGH NORTHERN LASALLE COUNTY AND INTO
THE FAR SOUTHWEST/SOUTHERN CHICAGO SUBURBAN AREA. INSTABILITY
APPEARS REALIZED FROM THE SURFACE...WITH 1000-1500 J/KG POOLED
ALONG THE BOUNDARY. WHILE IT IS DIFFICULT TO TELL WHERE SPECIFIC
SHORT WAVE IMPULSES ARE ACROSS THE MID- MISSISSIPPI VALLEY LIFTING
NORTHWARD...STORM COVERAGE AND INTENSITY HAS GRADUALLY INCREASED
ACROSS WESTERN ILLINOIS. WILL IN PARTICULAR BE WATCHING AS NORTH-
NORTHEASTWARD MOVING STORMS CROSS THE BOUNDARY /SUCH AS ONE IN
NORTHERN BUREAU COUNTY AS OF 540 PM/...WHERE A BRIEF TORNADO
THREAT WILL EXIST GIVEN 0-1KM SHEAR OF 20-25KT AND EFFECTIVE LOW-
LEVEL HELICITY OF 150-200 M2/S2. THE LOW VWP DATA /JUST NORTH OF
THE BOUNDARY/ VERIFIES THIS WITH STRONG TURNING AND SPEED
INCREASE. IT IS CHALLENGING TO TELL HOW LONG INTO THE EVENING A
TORNADO THREAT WILL EXIST...BUT GIVEN A ROBUST LOW-LEVEL JET OF
60 KT FORECAST TO DEVELOP...AND VWP DATA ALREADY SHOWING 45 KT
WINDS...WE FELT IT BEST TO GO THROUGH THE EVENING. THE LONGER INTO
THE EVENING THE STORM THREAT EXISTS THEN A THREAT MAY BUILD
SLIGHTLY EAST OF CURRENT WATCH...BUT CONFIDENCE IS LOW ON THIS AT
THIS POINT.

MTF

&&

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SHRA AND POSSIBLE TSRA THIS EVENING...AND SHRA AGAIN TONIGHT.

* WARM FRONT LIFTING THROUGH...SHIFTING WINDS FROM EAST TO SOUTH.

* STRONG AND GUSTY SOUTH WINDS TOMORROW MORNING.

LENNING

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM TO HIGH CONFIDENCE ON SHRA/TSRA TRENDS.

* MEDIUM CONFIDENCE REGARDING TIMING OF WIND SHIFT THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE OF STRONG AND GUSTY WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242208
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
508 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SHRA AND POSSIBLE TSRA THIS EVENING...AND SHRA AGAIN TONIGHT.

* WARM FRONT LIFTING THROUGH...SHIFTING WINDS FROM EAST TO SOUTH.

* STRONG AND GUSTY SOUTH WINDS TOMORROW MORNING.

LENNING

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM TO HIGH CONFIDENCE ON SHRA/TSRA TRENDS.

* MEDIUM CONFIDENCE REGARDING TIMING OF WIND SHIFT THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE OF STRONG AND GUSTY WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 242208
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
508 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SHRA AND POSSIBLE TSRA THIS EVENING...AND SHRA AGAIN TONIGHT.

* WARM FRONT LIFTING THROUGH...SHIFTING WINDS FROM EAST TO SOUTH.

* STRONG AND GUSTY SOUTH WINDS TOMORROW MORNING.

LENNING

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM TO HIGH CONFIDENCE ON SHRA/TSRA TRENDS.

* MEDIUM CONFIDENCE REGARDING TIMING OF WIND SHIFT THIS EVENING.

* MEDIUM TO HIGH CONFIDENCE OF STRONG AND GUSTY WINDS TOMORROW.

LENNING

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242039
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
339 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* SCT SHRA AND POSSIBLY AN ISOLD TSRA EXPECTED INTO LATE
  AFTERNOON...WITH A LESSER CHANCE THIS EVENING. PERIOD OF
  SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* HIGH CONFIDENCE SOME SHRA AND POSSIBLY BRIEF TSRA WILL AFFECT
  THE TERMINALS INTO LATE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN
  LESSER COVERAGE THIS EVENING. MEDIUM-HIGH CONFIDENCE IN SHRA-
  TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 242039
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
339 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* SCT SHRA AND POSSIBLY AN ISOLD TSRA EXPECTED INTO LATE
  AFTERNOON...WITH A LESSER CHANCE THIS EVENING. PERIOD OF
  SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* HIGH CONFIDENCE SOME SHRA AND POSSIBLY BRIEF TSRA WILL AFFECT
  THE TERMINALS INTO LATE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN
  LESSER COVERAGE THIS EVENING. MEDIUM-HIGH CONFIDENCE IN SHRA-
  TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
330 PM CDT

A WARM FRONT WILL LIFT NORTHWARD INTO THE SOUTHERN PART OF THE
LAKE THIS EVENING...OR POSSIBLY NOT UNTIL OVERNIGHT...BUT EITHER
WAY WINDS WILL TURN SOUTHERLY DURING THE NIGHT. HIGHER DEW POINT
AIR WILL ADVECT NORTHWARD ON THESE SOUTHERLY WINDS ALLOWING FOR
POTENTIAL FOG DEVELOPMENT. AS LOW PRESSURE LIFTS NORTH THROUGH
WISCONSIN ON MEMORIAL DAY MORNING....SOUTH TO SOUTHWEST WINDS
WILL ENCOMPASS THE ENTIRE LAKE. ALSO...WIND SPEEDS WILL RAPIDLY
INCREASE IN THE ILLINOIS AND INDIANA NEARSHORE WATERS...WITH
OFFSHORE WINDS REACHING GALE CRITERIA DURING THE MORNING AND
LASTING INTO AT LEAST EARLY AFTERNOON. OVER MUCH OF THE OPEN
WATERS...STABLE AIR WILL LIKELY KEEP THE STRONGEST WINDS FROM THE
SURFACE...ALTHOUGH STILL 20 TO 30 KT WINDS ARE EXPECTED AND
LASTING INTO MONDAY NIGHT.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 242003
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
303 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE
NEGATIVELY TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A
POTENT MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES
WHICH WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SUNDAY...

SCATTERED SHOWERS AND STORMS WILL LIKELY START THE MEMORIAL DAY
HOLIDAY BUT SHOULD BE MOVING QUICKLY NORTHEAST IN TANDEM WITH
DEEPENING LOW PRESSURE ADVANCING FROM NORTHEAST IA EARLY IN THE
MORNING TO NORTHERN WI BY MIDDAY. SHOWERS SHOULD END FROM SOUTHWEST
TO NORTHEAST BETWEEN 8 AM AND 11 AM FOR MOST LOCATIONS. THE BIGGER
STORY ON THE HOLIDAY WILL BE THE GUSTY WINDS ASSOCIATED WITH THIS
LOW...AS WELL AS WARMTH...WITH SOME LOCATIONS POSSIBLY REACHING
UPPER 80S.

THE SYNOPTIC SETUP IS IN PLACE FOR A THREE-FOUR HOUR PERIOD OF
STRONG WINDS MONDAY MORNING...WITH GLOBAL AND HIGH-RES MODELS
INDICATING 1.) SYSTEM DRY SLOT NOSE ADVANCING OVER THE
AREA...2.)STRONG SURFACE PRESSURE FALL/RISE COUPLET QUICKLY MOVING
THROUGH IN THE MORNING...AND 3.) STEEP LOW/LEVEL LAPSE RATES AND Q-
VECTOR DIVERGENCE INDICATING A PORTION OF THE LOW-LEVEL JET WINDS
WILL BE MIXED DOWN IN GUSTS. THE STRONGEST SOUTHWEST WINDS GUSTING
TO 40 TO 45 MPH WITH A POSSIBLE 1-2 HOUR TIME OF 50+ MPH GUSTS LOOK
TO BE BETWEEN 9 AM AND 2 PM. THIS IS IN THE IMMEDIATE WAKE OF THE
SHOWERS...THOUGH SOME OF THE LAST SHOWERS/STORMS COULD TAP SOME
OF THESE HIGHER WINDS WITH ISOLATED STRONG GUSTS BEFORE ENDING.
RIGHT NOW THE WIND FORECAST IS A LITTLE BELOW WIND ADVISORY
CRITERIA...BUT EVENING AND OVERNIGHT SHIFTS WILL HAVE TO CONSIDER
THIS POSSIBILITY LOOKING AT FURTHER GUIDANCE REGARDING MAGNITUDE AND
DURATION OF THESE WINDS...AS WELL AS TAKING INTO ACCOUNT THE HOLIDAY
AND AMOUNT OF OUTDOOR ACTIVITIES/PARADES.

THESE WINDS WILL TRANSPORT A STRONG THERMAL RIDGE INTO THE AREA.
SUBSIDENCE WITHIN THE DRY SLOT WILL LIKELY AID IN SCATTERING CLOUDS
BY EARLY AFTERNOON. SO SUN SHOULD FURTHER HEATING ON TOP OF THE LOW-
LEVEL WARM ADVECTION. GIVEN A MILD LOW TONIGHT...EXPECTING HIGHS TO
EASILY BE ABLE TO GET INTO THE 80S AREAWIDE. WITH SOME CENTRAL IL
LOCATIONS KNOCKING ON THE DOOR OF UPPER 80S TODAY...COULD ENVISION
THESE TYPE OF READINGS AND EVEN A 90 OR TWO SPREADING OVER
MUCH OF NORTHERN IL AND NORTHWEST IN ON MEMORIAL DAY...ALTHOUGH THE
INCREASED DEW POINTS ARE EXPECTED TO LIMIT THAT UPPER THRESHOLD.

WITH A VERY BROAD LONGWAVE TROUGH ACROSS THE WESTERN AND CENTRAL
U.S. GRADUALLY DEAMPLIFYING MIDWEEK...A GENERALLY UNSETTLED WEATHER
PATTERN CONTINUES THROUGH TUESDAY AND TUESDAY NIGHT. HEIGHT FALLS
AND JUST MORE FAVORABLE JET SUPPORT FOR LIFT WILL SPREAD OVER ON
TUESDAY. A SHORT WAVE TROUGH WITH A SLIGHT NEGATIVE TILT WILL BE IN
LINE WITH THIS...AND SUPPORT FOR SHOWERS AND AT LEAST SCATTERED
STORMS IS AGREED WELL UPON IN GUIDANCE. HAVE CONTINUED THE UPWARD
TREND WITH POPS. WITH THE RAIN AROUND...TEMPERATURES ON TUESDAY
LOOK TO BE AROUND 10 DEGREES COOLER THAN MONDAY.

BEYOND...THE MAIN REFINEMENTS WERE TO TRY TO INDICATE ANY TIMES
WHERE POPS MAY NOT NEED TO BE MENTIONED. WEDNESDAY AFTERNOON
THROUGH THURSDAY...AND POSSIBLY A LITTLE LONGER...LOOK TO BE A
PERIOD OF BUILDING HEIGHTS FOR MUCH OF THE AREA AND WOULD BE THE
WINDOW WHERE CHANCES OF RAIN WOULD SEEM SMALL. THE CHANCES FOR
PRECIPITATION INCREASE IN GLOBAL ENSEMBLES AS WE ENTER NEXT
WEEKEND...WITH THE 12Z GFS PARTICULARLY WET. AT THIS TIME...WPC
DOES HAVE AROUND AN INCH IN THEIR DETERMINISTIC DAY 6-7 GUIDANCE.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* SCT SHRA AND POSSIBLY AN ISOLD TSRA EXPECTED INTO LATE
  AFTERNOON...WITH A LESSER CHANCE THIS EVENING. PERIOD OF
  SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* HIGH CONFIDENCE SOME SHRA AND POSSIBLY BRIEF TSRA WILL AFFECT
  THE TERMINALS INTO LATE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN
  LESSER COVERAGE THIS EVENING. MEDIUM-HIGH CONFIDENCE IN SHRA-
  TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...

TO BE ISSUED SHORTLY.

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241920
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
220 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE NEGATIVELY
TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A POTENT
MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES WHICH
WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* SCT SHRA AND POSSIBLY AN ISOLD TSRA EXPECTED INTO LATE
  AFTERNOON...WITH A LESSER CHANCE THIS EVENING. PERIOD OF
  SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* HIGH CONFIDENCE SOME SHRA AND POSSIBLY BRIEF TSRA WILL AFFECT
  THE TERMINALS INTO LATE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN
  LESSER COVERAGE THIS EVENING. MEDIUM-HIGH CONFIDENCE IN SHRA-
  TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241920
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
220 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTORMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT
ACROSS FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM
I-39 WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS
IN BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE
TO FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE NEGATIVELY
TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A POTENT
MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES WHICH
WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* SCT SHRA AND POSSIBLY AN ISOLD TSRA EXPECTED INTO LATE
  AFTERNOON...WITH A LESSER CHANCE THIS EVENING. PERIOD OF
  SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 20Z...

A NARROW CORRIDOR OF SHOWERS AND SOME ISOLD TS HAS DEVELOPED FROM
RPJ SOUTH TO NEAR PNT AND IS LIFTING NNE. TS MAY BECOME LESS
PREVALENT AS IT MOVES FURTHER NORTH BUT HAVE ADDED TEMP SHRA WITH
VSBY RESTRICTION IN DOWNPOUR TO ORD/MDW/DPA FOR A FEW HOURS.
OTHERWISE WARM FRONT CONTINUES TO LIFT NORTH AND WILL BRING A
SHIFT TO SOUTH WINDS AS IT MOVES ACROSS THE TERMINALS LATE THIS
AFTERNOON/EARLY THIS EVENING.

FROM 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* HIGH CONFIDENCE SOME SHRA AND POSSIBLY BRIEF TSRA WILL AFFECT
  THE TERMINALS INTO LATE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN
  LESSER COVERAGE THIS EVENING. MEDIUM-HIGH CONFIDENCE IN SHRA-
  TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241910
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTROMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT ACROSS
FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM I-39
WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS IN
BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE TO
FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE NEGATIVELY
TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A POTENT
MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES WHICH
WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* ISOLD-SCT SHRA POSSIBLE THROUGH THE AFTERNOON WITH A LESSER
  CHANCE THIS EVENING. PERIOD OF SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* MEDIUM CONFIDENCE THAT SHRA COVERAGE WILL BE ISOLD-SCT THROUGH
  THE AFTERNOON WITH LESSER COVERAGE THIS EVENING. MEDIUM-HIGH
  CONFIDENCE IN SHRA-TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241910
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTROMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT ACROSS
FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM I-39
WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS IN
BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE TO
FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE NEGATIVELY
TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A POTENT
MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES WHICH
WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* ISOLD-SCT SHRA POSSIBLE THROUGH THE AFTERNOON WITH A LESSER
  CHANCE THIS EVENING. PERIOD OF SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* MEDIUM CONFIDENCE THAT SHRA COVERAGE WILL BE ISOLD-SCT THROUGH
  THE AFTERNOON WITH LESSER COVERAGE THIS EVENING. MEDIUM-HIGH
  CONFIDENCE IN SHRA-TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 PM CDT SUN MAY 24 2015

.UPDATE...

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.
ILLINOIS WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE
MOST LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR.
ISOLATED THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM
FRONT WHICH WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN
CHICAGOLAND COUNTIES.

WE ALSO INCREASED WINDS FOR MONDAY MORNING. THERE LOOKS TO BE A
SURGE OF STRONGER WIND GUSTS DURING THE MORNING HOURS WHERE GUSTS
TO 40 MPH ARE LIKELY...WITH LOCALIZED HIGHER GUSTS. MONDAY WILL BE
A WINDY DAY...BUT EXPECT WINDS TO COME DOWN SOME IN THE AFTERNOON.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* ISOLD-SCT SHRA POSSIBLE THROUGH THE AFTERNOON WITH A LESSER
  CHANCE THIS EVENING. PERIOD OF SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* MEDIUM CONFIDENCE THAT SHRA COVERAGE WILL BE ISOLD-SCT THROUGH
  THE AFTERNOON WITH LESSER COVERAGE THIS EVENING. MEDIUM-HIGH
  CONFIDENCE IN SHRA-TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

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000
FXUS63 KLOT 241759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 PM CDT SUN MAY 24 2015

.UPDATE...

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.
ILLINOIS WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE
MOST LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR.
ISOLATED THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM
FRONT WHICH WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN
CHICAGOLAND COUNTIES.

WE ALSO INCREASED WINDS FOR MONDAY MORNING. THERE LOOKS TO BE A
SURGE OF STRONGER WIND GUSTS DURING THE MORNING HOURS WHERE GUSTS
TO 40 MPH ARE LIKELY...WITH LOCALIZED HIGHER GUSTS. MONDAY WILL BE
A WINDY DAY...BUT EXPECT WINDS TO COME DOWN SOME IN THE AFTERNOON.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* ISOLD-SCT SHRA POSSIBLE THROUGH THE AFTERNOON WITH A LESSER
  CHANCE THIS EVENING. PERIOD OF SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* MEDIUM CONFIDENCE THAT SHRA COVERAGE WILL BE ISOLD-SCT THROUGH
  THE AFTERNOON WITH LESSER COVERAGE THIS EVENING. MEDIUM-HIGH
  CONFIDENCE IN SHRA-TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241652
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1152 AM CDT SUN MAY 24 2015

.UPDATE...1135 AM CDT

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.  ILLINOIS
WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE MOST
LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR. ISOLATED
THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM FRONT WHICH
WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN CHICAGOLAND
COUNTIES.

WE ALSO INCREASED WINDS FOR MONDAY MORNING. THERE LOOKS TO BE A
SURGE OF STRONGER WIND GUSTS DURING THE MORNING HOURS WHERE GUSTS
TO 40 MPH ARE LIKELY...WITH LOCALIZED HIGHER GUSTS. MONDAY WILL BE
A WINDY DAY...BUT EXPECT WINDS TO COME DOWN SOME IN THE AFTERNOON.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241652
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1152 AM CDT SUN MAY 24 2015

.UPDATE...1135 AM CDT

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.  ILLINOIS
WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE MOST
LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR. ISOLATED
THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM FRONT WHICH
WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN CHICAGOLAND
COUNTIES.

WE ALSO INCREASED WINDS FOR MONDAY MORNING. THERE LOOKS TO BE A
SURGE OF STRONGER WIND GUSTS DURING THE MORNING HOURS WHERE GUSTS
TO 40 MPH ARE LIKELY...WITH LOCALIZED HIGHER GUSTS. MONDAY WILL BE
A WINDY DAY...BUT EXPECT WINDS TO COME DOWN SOME IN THE AFTERNOON.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241642
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1142 AM CDT SUN MAY 24 2015

.UPDATE...
1135 AM CDT

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.  ILLINOIS
WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE MOST
LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR. ISOLATED
THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM FRONT WHICH
WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN CHICAGOLAND
COUNTIES.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241642
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1142 AM CDT SUN MAY 24 2015

.UPDATE...
1135 AM CDT

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.  ILLINOIS
WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE MOST
LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR. ISOLATED
THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM FRONT WHICH
WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN CHICAGOLAND
COUNTIES.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 241642
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1142 AM CDT SUN MAY 24 2015

.UPDATE...
1135 AM CDT

VERY SHARP WARM FRONT HAS SET UP ACROSS THE AREA THIS AFTERNOON
AND LOOKS TO HOLD TIGHT THROUGH MID TO LATE AFTERNOON. LIGHT RAIN
ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA WILL DRIFT
THROUGH IN THE COMING HOURS. MEANWHILE...NO REAL STRONG SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE REMAINDER OF TODAY...BUT WE DO
HAVE MOIST LOW LEVEL SOUTHWEST FLOW THAT WILL CONTRIBUTE TO
SCATTERED SHOWER DEVELOPMENT THROUGH THE AFTERNOON HOURS...WHICH
IS ONGOING ALREADY ONGOING WEST OF I-39 AND ALONG THE I-55
CORRIDOR IN MCLEAN COUNTY...JUST SOUTHWEST OF FORD/LIVINGSTON.  ILLINOIS
WILL BE THE FAVORED AREA FOR SCATTERED SHOWERS...WITH THE MOST
LIKELY AREAS BEING IN THE VICINITY OF THE I-39 CORRIDOR. ISOLATED
THUNDERSTORMS WILL REMAIN CONFINED SOUTH OF THE WARM FRONT WHICH
WILL BE INCHING ITS WAY NORTHWARD TO THE SOUTHERN CHICAGOLAND
COUNTIES.

KMD

&&

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1112 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1112 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1112 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* SPOTTY LIGHT RAIN/SPRINKLES THE REST OF THE MORNING BUT
  SHOWER COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 16Z...
THE BULK OF THE PRECIP IS LIFTING NORTH OF THE TERMINALS WITH
LINGERING LIGHT RAIN/SPRINKLES...MAINLY AFFECTING RFD. SHRA
COVERAGE IS EXPECTED TO INCREASE SOMEWHAT ACROSS NORTH-CENTRAL IL
INTO THE AFTERNOON WITH RADAR TRENDS TO THE SOUTH SUPPORTING THIS.
A WARM FRONT DOWN TOWARDS PNT-RZL WILL LIFT NORTHWARD INTO THE
AFTERNOON AND THERE IS SUPPORT FOR IT TO BECOME BETTER FOCUSED
WHICH WOULD YIELD A MORE EASTERLY WIND COMPONENT TO ITS NORTH
ACROSS THE TERMINALS THROUGH MID AFTERNOON. HAVE TRENDED MORE
EASTERLY ON THE WIND AT ORD/MDW/DPA FOR SEVERAL HOURS BEFORE WINDS
TURN SOUTHERLY LATER THIS AFTERNOON. EXPECT THAT WIND GUSTS WOULD
BE HELD OFF UNTIL WINDS TURN SOUTHERLY. GIVEN THE POTENTIAL
INFLUENCE OF THE LAKE...A NORTHEAST DIRECTION IS NOT OUT OF THE
QUESTION THROUGH EARLY AFTERNOON.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION
  THROUGH MUCH OF THE AFTERNOON...EAST MAY PREVAIL MIDDAY/EARLY
  AFTERNOON. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO SOUTHERLY
  WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241425
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
925 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* LITTLE IN THE WAY OF SHRA THROUGH THE REST OF THE MORNING BUT
  COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 14Z...
INITIAL BAND OF SHRA HAS LIFTED NORTHEAST OF ALL TERMINALS EXCEPT
FOR RFD. RFD WILL LIKELY CONTINUE TO SEE A FEW HOURS OF STEADIER
SHRA WITH COVERAGE POSSIBLY WANING A BIT TOWARD MIDDAY. OTHERWISE
EXCEPT THAT RFD WILL SEE THE GREATEST COVERAGE OF SHRA THROUGH THE
DAY. EXPECT THAT THERE WILL BE AN INCREASE IN COVERAGE OF SHRA
ACROSS NORTHEAST IL AND A LESSER EXTENT ACROSS NORTHWEST IN.
FORCING WILL BE RATHER BROAD SUPPORTING SCATTERED COVERAGE VS.
SOMETHING BETTER ORGANIZED AND EXPECT THAT OCCURRENCE AT ANY TAF
SITE WOULD BE INTERMITTENT FOR THE MOST PART. CHANCES WILL
STEADILY INCREASE THROUGH THE AFTERNOON. TSRA POTENTIAL IS LIMITED
THROUGH THE AFTERNOON AND EVEN THIS EVENING. THE CHANCE DOES
MODESTLY INCREASE THIS EVENING THOUGH REMAINS LOW / NOT ZERO/ SO
HAVE REMOVED TSRA MENTION FOR MUCH OF THE EVENING HOURS EXCEPT FOR
RFD.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION THROUGH
  MUCH OF THE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN TIMING OF
  SPEEDS TOPPING 10 KT. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO
  SOUTHERLY WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM-HIGH CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

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000
FXUS63 KLOT 241425
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
925 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* LITTLE IN THE WAY OF SHRA THROUGH THE REST OF THE MORNING BUT
  COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 14Z...
INITIAL BAND OF SHRA HAS LIFTED NORTHEAST OF ALL TERMINALS EXCEPT
FOR RFD. RFD WILL LIKELY CONTINUE TO SEE A FEW HOURS OF STEADIER
SHRA WITH COVERAGE POSSIBLY WANING A BIT TOWARD MIDDAY. OTHERWISE
EXCEPT THAT RFD WILL SEE THE GREATEST COVERAGE OF SHRA THROUGH THE
DAY. EXPECT THAT THERE WILL BE AN INCREASE IN COVERAGE OF SHRA
ACROSS NORTHEAST IL AND A LESSER EXTENT ACROSS NORTHWEST IN.
FORCING WILL BE RATHER BROAD SUPPORTING SCATTERED COVERAGE VS.
SOMETHING BETTER ORGANIZED AND EXPECT THAT OCCURRENCE AT ANY TAF
SITE WOULD BE INTERMITTENT FOR THE MOST PART. CHANCES WILL
STEADILY INCREASE THROUGH THE AFTERNOON. TSRA POTENTIAL IS LIMITED
THROUGH THE AFTERNOON AND EVEN THIS EVENING. THE CHANCE DOES
MODESTLY INCREASE THIS EVENING THOUGH REMAINS LOW / NOT ZERO/ SO
HAVE REMOVED TSRA MENTION FOR MUCH OF THE EVENING HOURS EXCEPT FOR
RFD.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION THROUGH
  MUCH OF THE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN TIMING OF
  SPEEDS TOPPING 10 KT. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO
  SOUTHERLY WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM-HIGH CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241425
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
925 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* LITTLE IN THE WAY OF SHRA THROUGH THE REST OF THE MORNING BUT
  COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 14Z...
INITIAL BAND OF SHRA HAS LIFTED NORTHEAST OF ALL TERMINALS EXCEPT
FOR RFD. RFD WILL LIKELY CONTINUE TO SEE A FEW HOURS OF STEADIER
SHRA WITH COVERAGE POSSIBLY WANING A BIT TOWARD MIDDAY. OTHERWISE
EXCEPT THAT RFD WILL SEE THE GREATEST COVERAGE OF SHRA THROUGH THE
DAY. EXPECT THAT THERE WILL BE AN INCREASE IN COVERAGE OF SHRA
ACROSS NORTHEAST IL AND A LESSER EXTENT ACROSS NORTHWEST IN.
FORCING WILL BE RATHER BROAD SUPPORTING SCATTERED COVERAGE VS.
SOMETHING BETTER ORGANIZED AND EXPECT THAT OCCURRENCE AT ANY TAF
SITE WOULD BE INTERMITTENT FOR THE MOST PART. CHANCES WILL
STEADILY INCREASE THROUGH THE AFTERNOON. TSRA POTENTIAL IS LIMITED
THROUGH THE AFTERNOON AND EVEN THIS EVENING. THE CHANCE DOES
MODESTLY INCREASE THIS EVENING THOUGH REMAINS LOW / NOT ZERO/ SO
HAVE REMOVED TSRA MENTION FOR MUCH OF THE EVENING HOURS EXCEPT FOR
RFD.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION THROUGH
  MUCH OF THE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN TIMING OF
  SPEEDS TOPPING 10 KT. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO
  SOUTHERLY WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM-HIGH CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241425
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
925 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE
LOWER 60S. LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING
INTO THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING
CLOSE TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* EAST TO SOUTHEAST WINDS INCREASING IN SPEED EARLY AFTERNOON THEN
  TRENDING SOUTH LATE AFTERNOON OR EARLY EVENING.

* LITTLE IN THE WAY OF SHRA THROUGH THE REST OF THE MORNING BUT
  COVERAGE INCREASES THROUGH THE AFTERNOON.

* CHANCE FOR EMBEDDED TSRA INCREASES MARGINALLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//DISCUSSION...UPDATED 14Z...
INITIAL BAND OF SHRA HAS LIFTED NORTHEAST OF ALL TERMINALS EXCEPT
FOR RFD. RFD WILL LIKELY CONTINUE TO SEE A FEW HOURS OF STEADIER
SHRA WITH COVERAGE POSSIBLY WANING A BIT TOWARD MIDDAY. OTHERWISE
EXCEPT THAT RFD WILL SEE THE GREATEST COVERAGE OF SHRA THROUGH THE
DAY. EXPECT THAT THERE WILL BE AN INCREASE IN COVERAGE OF SHRA
ACROSS NORTHEAST IL AND A LESSER EXTENT ACROSS NORTHWEST IN.
FORCING WILL BE RATHER BROAD SUPPORTING SCATTERED COVERAGE VS.
SOMETHING BETTER ORGANIZED AND EXPECT THAT OCCURRENCE AT ANY TAF
SITE WOULD BE INTERMITTENT FOR THE MOST PART. CHANCES WILL
STEADILY INCREASE THROUGH THE AFTERNOON. TSRA POTENTIAL IS LIMITED
THROUGH THE AFTERNOON AND EVEN THIS EVENING. THE CHANCE DOES
MODESTLY INCREASE THIS EVENING THOUGH REMAINS LOW / NOT ZERO/ SO
HAVE REMOVED TSRA MENTION FOR MUCH OF THE EVENING HOURS EXCEPT FOR
RFD.

MDB

FROM 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN AN EAST TO SOUTHEAST WIND DIRECTION THROUGH
  MUCH OF THE AFTERNOON. MEDIUM-HIGH CONFIDENCE IN TIMING OF
  SPEEDS TOPPING 10 KT. MEDIUM CONFIDENCE IN TIMING OF SHIFT TO
  SOUTHERLY WINDS.

* HIGH CONFIDENCE IN A LULL IN PRECIP THROUGH THE MORNING WITH
  MEDIUM-HIGH CONFIDENCE IN INCREASING SHRA CHANCES THROUGH THE
  AFTERNOON. LOW-MEDIUM CONFIDENCE IN HOW MUCH COVERAGE THERE WILL
  BE THIS AFTERNOON.

* MEDIUM-HIGH CONFIDENCE THAT TSRA POTENTIAL IS MINIMAL THROUGH
  MID AFTERNOON AND THAT IT INCREASES SLIGHTLY THIS EVENING AND
  MORESO TONIGHT.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SCATTERED SHOWERS THIS MORNING.

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* INCREASING CHANCES FOR SHRA WITH POSSIBLE TSRA LATE EVENING
  THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 241140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SCATTERED SHOWERS THIS MORNING.

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* INCREASING CHANCES FOR SHRA WITH POSSIBLE TSRA LATE EVENING
  THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SCATTERED SHOWERS THIS MORNING.

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* INCREASING CHANCES FOR SHRA WITH POSSIBLE TSRA LATE EVENING
  THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 241140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SCATTERED SHOWERS THIS MORNING.

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* INCREASING CHANCES FOR SHRA WITH POSSIBLE TSRA LATE EVENING
  THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 12Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THIS MORNING. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY AND THEN
VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE NORTH INTO
WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT PUSHES TO THE
NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE AS A
STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF MOISTURE
INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS COVERAGE
INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING WILL
STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO WITH
VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA IN THE MORNING...WITH INCREASING CHANCES
  FOR SHRA WITH POSSIBLE TSRA LATE EVENING THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA IN THE MORNING...WITH INCREASING CHANCES
  FOR SHRA WITH POSSIBLE TSRA LATE EVENING THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA IN THE MORNING...WITH INCREASING CHANCES
  FOR SHRA WITH POSSIBLE TSRA LATE EVENING THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING...WITH GUSTS
  UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA IN THE MORNING...WITH INCREASING CHANCES
  FOR SHRA WITH POSSIBLE TSRA LATE EVENING THROUGH THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT SUN MAY 24 2015

.SHORT TERM...
310 AM CDT

SUNDAY AND SUNDAY NIGHT...

MAIN ISSUES FOR THE SHORT TERM FORECAST PERIOD WILL BE RAMPING UP
PCPN CHANCES AS WELL AS HIGH TEMPS FOR TODAY...ESPECIALLY ALONG THE
ILLINOIS LAKE MICHIGAN SHORE.  A LARGE AREA OF HIGH PRESSURE
CONTINUES TO SLOWLY SLIDE OFF THE MID ATLANTIC COAST WITH A RIDGE
AXIS EXTENDING BACK THROUGH THE UPPER MISSISSIPPI VALLEY.
MEANWHILE...LEE CYCLOGENESIS SLOWLY PERSISTS OVER ERN CO/NM. A
RETURN FLOW OF MOISTURE IS SETTING UP OVER THE CNTRL CONUS IN
GENERALLY SELY-SLY AROUND THE WRN PERIPHERY OF THE DEPARTING HIGH.
ALSO...A WEAK WARM FRONT/TROUGH APPEARS TO BE SEEING UP ACROSS THE
OHIO VALLEY WEST THROUGH SRN MO.  WINDS TO THE NORTH OF THE BOUNDARY
ARE PREVAILING SELY WITH PREVAILING SLY WINDS TO THE SOUTH. THE SELY
WINDS WILL CONTINUE TO KEEP THE IL SHORE OF LAKE MICHIGAN A BIT
COOLER THAN INLAND LOCATIONS.  HOWEVER...THE BOUNDARY IS EXPECTED TO
MOVE NORTH THROUGH THE DAY...PUTTING THE ENTIRE REGION UNDER SLY
FLOW EVENTUALLY.  THE MAIN IMPACT WILL BE ON TEMPERATURES.  WITH
LITTLE CHANGE TO THE OVERALL PATTERN...ANOTHER WARM DAY IS EXPECTED
FOR TODAY...THOUGH MORE EXTENSIVE CLOUD COVER COULD KEEP MAX TEMPS
LOWER BY A DEGREE OR 2.  DO NOT EXPECT A LAKE BREEZE TO
FORM...ESPECIALLY WITH STRENGTHENING WINDS OF 10-15 MPH...BUT RATHER
WITH SYNOPTICALLY SOUTHEAST FLOW PERSISTING INTO THE EARLY
AFTERNOON...THE ILLINOIS SHORE SHOULD BE COOLER THAN WELL
INLAND...BUT AS WINDS TURN SLY BY EARLY AFTERNOON OVER THE COOK
COUNTY SHORE...TEMPS SHOULD REBOUND INTO THE LOW 70S.  LAKE COUNTY
IL WILL REMAIN UNDER THE COOLER SELY FLOW A BIT LONGER...KEEPING THE
WAUKEEGAN AREA COOLER THROUGH THE DAY...WITH HIGHS ONLY IN THE LOWER
60S.  LOCATIONS WELL INLAND SHOULD SEE MAX TEMPS TODAY RISING INTO
THE MIDDLE TO UPPER 70S...WITH THE PONTIAC METRO AREA HITTING CLOSE
TO 80F.

PCPN CHANCES FOR TODAY WILL BE A BIT TRICKY.  A WAVE OF SCT SHOWERS
IS MOVING NWD THROUGH WRN IL...ASSOCIATED WITH A WEAK SHORTWAVE
TRACKING UP THE WRN SIDE OF THE UPPER RIDGE WHICH IS ORIENTED FROM
THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THERE IS A
CHANCE FOR SOME OF THESE SHOWERS TO BRING SOME LIGHT RAIN TO THE
NWRN PORTIONS OF THE CWA...ALONG AND WEST OF THE I-39
CORRIDOR...INCLUDING THE ROCKFORD AREA.  OTHERWISE...THE GREATER
PCPN CHANCES WILL HAVE TO WAIT FOR A MUCH STRONGER SHORTWAVE
EXPECTED TO LIFT OUT OF THE SOUTH HIGH PLAINS LATER THIS MORNING.
THIS WAVE WILL TRACK NNELY TO THE UPPER MISSOURI VALLEY BY EARLY
THIS EVENING AND THEN AS THE UPPER RIDGE IS FORCES EWD...WILL THEN
TURN MORE NELY...REACHING THE MIDDLE MISSISSIPPI VALLEY LATE
TONIGHT.  THE MODEL GUIDANCE INDICATES A FEW STRONG LOW LEVEL JET OF
50-55KT DIRECTED INTO NRN IL LATE TONIGHT AS WELL.  THE STRONG LOW
LEVEL JET WILL HELP PUMP UP DEEP LAYER MOISTURE OVER THE REGION WITH
PWATS CLIMBING TO ARND 1.8 INCHES THIS EVENING.  THE TRICKER PARTS
TO THE WX/POP FORECAST HAS BEEN WHERE TO FOCUS THE CATEGORICAL POPS
AND HOW FAR EAST TO SPREAD THE HIGHER POPS AND HOW MUCH THUNDER TO
INDICATE WITHING THE WX.  HAVE LARGELY CONFINED THE CATEGORICAL POPS
TO THE VCNTY OF THE UPPER SHORTWAVE...OVER NWRN IL...INCLUDING THE
ROCKFORD AREA...BUT HAVE DROPPED OFF POPS TO THE SOUTHEAST...AWAY
FROM THE STRONGEST UPPER FORCING.  WHILE CURRENT THINKING IS THAT
MUCH OF THE CWA SHOULD SEE SOME MEASURABLE PCPN AT SOME POINT...IT
IS MOST LIKELY THAT THE ERN PORTIONS OF THE CWA...INCLUDING THE
CHICAGO METRO AREA AND NWRN INDIANA WILL LIKELY NOT SEE THE PCPN
UNTIL LATE TONIGHT OR EARLY TOMORROW MORNING.  THE OTHER CONCERN IS
THE THUNDER CHANCES.  FEEL THAT THE GREATER CHANCES WILL ALSO BE
CLOSER TO THE UPPER FORCING...OVER THE WRN PORTIONS OF THE CWA...BUT
THERE IS A CHANCE THAT THE ERN PORTIONS OF THE CWA COULD SEE SOME
ISOLD-SCT TS AS WELL LATE TONIGHT.  CURRENTLY...THE GREATEST
SENSIBLE WEATHER THREAT FROM THIS SYSTEM WILL BE LOCALLY HEAVY
RAINFALL DUE TO THE ANOMALOUSLY HIGH PWATS.  PER THE DVN PWAT
CLIMATOLOGY FOR MID TO LATE MAY...THE EXPECTED 1.75 INCH PWAT
FORECAST IS NEAR THE 99TH PERCENTILE.  SO...SOME OF THE STRONGER
SHRA/TSRA THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY
HEAVY RAINFALL.

KREIN

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
245 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
245 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240729
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240729
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240729
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1258 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1258 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1258 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1258 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

//DISCUSSION...UPDATED 06Z...

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240257
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
957 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SOUTHEAST WINDS INCREASING TO 10 KT+ BY EARLY AFTERNOON SUNDAY.

* CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING CHANCES
  INCLUDING TSRA LATE IN THE DAY AND MORE SO AFTER DARK.


//DISCUSSION...UPDATED 00Z...

THE LAKE BREEZE BOUNDARY WILL CONTINUE TO INCH WESTWARD BEFORE
FADING AROUND OR SOON AFTER SUNDOWN. AS THAT OCCURS...THE EASTERLY
WINDS AT ORD AND MDW WILL EASE IN SPEED AND GRADUALLY VEER. SO 10
KT+ SPEEDS SHOULD BE FADING BETWEEN 01Z-02Z. OTHERWISE A QUIET
NIGHT IS IN STORE FOR AREA TAF SITES.

THE SUNDAY FORECAST IS CHALLENGING AS THERE ARE CHANCES FOR LIGHT
SHRA THROUGH MID AFTERNOON AND THEN CHANCES FOR SHRA/TSRA AFTER
THAT POINT. ONGOING WIDESPREAD STORMS ACROSS THE SOUTHERN PLAINS
ARE LIKELY TO HOLD BACK THE ELEVATED WARM FRONT AND ASSOCIATED
MOISTURE RETURN THROUGH TONIGHT AND EVEN INTO SUNDAY. THIS MAY BE
ENOUGH TO PREVENT MUCH SHOWER COVERAGE IN THE AFTERNOON AND EVEN
THE EVENING. FEEL RFD HAS THE BEST CHANCES FOR GETTING INTO SOME
CONVECTIVE ACTIVITY LATE IN THE DAY AND INTO SUNDAY
EVENING...WHILE AREAWIDE OVERNIGHT SUNDAY. OVERALL CONFIDENCE IS
LOW ON SPECIFIC TIMING AND COVERAGE DURING THE DAY SUNDAY...BUT
HAVE FELT A LITTLE STRONGER LEANING TOWARD THE MAINLY DRY ROUTE
DURING THE DAY FOR CHICAGO AREA TAF SITES.

WINDS ON THE REGIONAL SCALE WILL BECOME SOUTHEAST ON SUNDAY AND
GRADUALLY INCREASE IN SPEED WITH THE PRESSURE GRADIENT. THE
DIRECTION WILL FAVOR A LAKE BREEZE AGAIN IN NORTHEAST
ILLINOIS...WHICH WOULD TURN WINDS MORE DUE EASTERLY IF IT CAN
REACH ORD AND MDW. AT THIS TIME HAVE HELD MORE OF A SOUTHEAST
WIND IN THE TAFS...WHICH SHOULD IN ITSELF BE OVER 10 KT WITH SOME
PERIODIC GUSTS.


//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN WINDS ON SUNDAY AND TIMING OF 10+ KTS.

* HIGH THAT ANY TSRA CHANCES WOULD BE AFTER 21Z ON SUNDAY...BUT
  LOW ON SHRA TIMING AND COVERAGE ON SUNDAY AND SUNDAY EVENING.


//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 240257
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
957 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SOUTHEAST WINDS INCREASING TO 10 KT+ BY EARLY AFTERNOON SUNDAY.

* CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING CHANCES
  INCLUDING TSRA LATE IN THE DAY AND MORE SO AFTER DARK.


//DISCUSSION...UPDATED 00Z...

THE LAKE BREEZE BOUNDARY WILL CONTINUE TO INCH WESTWARD BEFORE
FADING AROUND OR SOON AFTER SUNDOWN. AS THAT OCCURS...THE EASTERLY
WINDS AT ORD AND MDW WILL EASE IN SPEED AND GRADUALLY VEER. SO 10
KT+ SPEEDS SHOULD BE FADING BETWEEN 01Z-02Z. OTHERWISE A QUIET
NIGHT IS IN STORE FOR AREA TAF SITES.

THE SUNDAY FORECAST IS CHALLENGING AS THERE ARE CHANCES FOR LIGHT
SHRA THROUGH MID AFTERNOON AND THEN CHANCES FOR SHRA/TSRA AFTER
THAT POINT. ONGOING WIDESPREAD STORMS ACROSS THE SOUTHERN PLAINS
ARE LIKELY TO HOLD BACK THE ELEVATED WARM FRONT AND ASSOCIATED
MOISTURE RETURN THROUGH TONIGHT AND EVEN INTO SUNDAY. THIS MAY BE
ENOUGH TO PREVENT MUCH SHOWER COVERAGE IN THE AFTERNOON AND EVEN
THE EVENING. FEEL RFD HAS THE BEST CHANCES FOR GETTING INTO SOME
CONVECTIVE ACTIVITY LATE IN THE DAY AND INTO SUNDAY
EVENING...WHILE AREAWIDE OVERNIGHT SUNDAY. OVERALL CONFIDENCE IS
LOW ON SPECIFIC TIMING AND COVERAGE DURING THE DAY SUNDAY...BUT
HAVE FELT A LITTLE STRONGER LEANING TOWARD THE MAINLY DRY ROUTE
DURING THE DAY FOR CHICAGO AREA TAF SITES.

WINDS ON THE REGIONAL SCALE WILL BECOME SOUTHEAST ON SUNDAY AND
GRADUALLY INCREASE IN SPEED WITH THE PRESSURE GRADIENT. THE
DIRECTION WILL FAVOR A LAKE BREEZE AGAIN IN NORTHEAST
ILLINOIS...WHICH WOULD TURN WINDS MORE DUE EASTERLY IF IT CAN
REACH ORD AND MDW. AT THIS TIME HAVE HELD MORE OF A SOUTHEAST
WIND IN THE TAFS...WHICH SHOULD IN ITSELF BE OVER 10 KT WITH SOME
PERIODIC GUSTS.


//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN WINDS ON SUNDAY AND TIMING OF 10+ KTS.

* HIGH THAT ANY TSRA CHANCES WOULD BE AFTER 21Z ON SUNDAY...BUT
  LOW ON SHRA TIMING AND COVERAGE ON SUNDAY AND SUNDAY EVENING.


//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 240257
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
957 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SOUTHEAST WINDS INCREASING TO 10 KT+ BY EARLY AFTERNOON SUNDAY.

* CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING CHANCES
  INCLUDING TSRA LATE IN THE DAY AND MORE SO AFTER DARK.


//DISCUSSION...UPDATED 00Z...

THE LAKE BREEZE BOUNDARY WILL CONTINUE TO INCH WESTWARD BEFORE
FADING AROUND OR SOON AFTER SUNDOWN. AS THAT OCCURS...THE EASTERLY
WINDS AT ORD AND MDW WILL EASE IN SPEED AND GRADUALLY VEER. SO 10
KT+ SPEEDS SHOULD BE FADING BETWEEN 01Z-02Z. OTHERWISE A QUIET
NIGHT IS IN STORE FOR AREA TAF SITES.

THE SUNDAY FORECAST IS CHALLENGING AS THERE ARE CHANCES FOR LIGHT
SHRA THROUGH MID AFTERNOON AND THEN CHANCES FOR SHRA/TSRA AFTER
THAT POINT. ONGOING WIDESPREAD STORMS ACROSS THE SOUTHERN PLAINS
ARE LIKELY TO HOLD BACK THE ELEVATED WARM FRONT AND ASSOCIATED
MOISTURE RETURN THROUGH TONIGHT AND EVEN INTO SUNDAY. THIS MAY BE
ENOUGH TO PREVENT MUCH SHOWER COVERAGE IN THE AFTERNOON AND EVEN
THE EVENING. FEEL RFD HAS THE BEST CHANCES FOR GETTING INTO SOME
CONVECTIVE ACTIVITY LATE IN THE DAY AND INTO SUNDAY
EVENING...WHILE AREAWIDE OVERNIGHT SUNDAY. OVERALL CONFIDENCE IS
LOW ON SPECIFIC TIMING AND COVERAGE DURING THE DAY SUNDAY...BUT
HAVE FELT A LITTLE STRONGER LEANING TOWARD THE MAINLY DRY ROUTE
DURING THE DAY FOR CHICAGO AREA TAF SITES.

WINDS ON THE REGIONAL SCALE WILL BECOME SOUTHEAST ON SUNDAY AND
GRADUALLY INCREASE IN SPEED WITH THE PRESSURE GRADIENT. THE
DIRECTION WILL FAVOR A LAKE BREEZE AGAIN IN NORTHEAST
ILLINOIS...WHICH WOULD TURN WINDS MORE DUE EASTERLY IF IT CAN
REACH ORD AND MDW. AT THIS TIME HAVE HELD MORE OF A SOUTHEAST
WIND IN THE TAFS...WHICH SHOULD IN ITSELF BE OVER 10 KT WITH SOME
PERIODIC GUSTS.


//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN WINDS ON SUNDAY AND TIMING OF 10+ KTS.

* HIGH THAT ANY TSRA CHANCES WOULD BE AFTER 21Z ON SUNDAY...BUT
  LOW ON SHRA TIMING AND COVERAGE ON SUNDAY AND SUNDAY EVENING.


//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 232337
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* EASTERLY WINDS AROUND 10 KT THROUGH SUNSET BEFORE DIMINISHING IN
  SPEED AND SLOWLY VEERING.

* SOUTHEAST WINDS INCREASING TO 10 KT+ BY EARLY AFTERNOON SUNDAY.

* CHANCE OF -SHRA MID-LATE SUNDAY MORNING THEN INCREASING CHANCES
  INCLUDING TSRA LATE IN THE DAY AND MORE SO AFTER DARK.


//DISCUSSION...UPDATED 00Z...

THE LAKE BREEZE BOUNDARY WILL CONTINUE TO INCH WESTWARD BEFORE
FADING AROUND OR SOON AFTER SUNDOWN. AS THAT OCCURS...THE EASTERLY
WINDS AT ORD AND MDW WILL EASE IN SPEED AND GRADUALLY VEER. SO 10
KT+ SPEEDS SHOULD BE FADING BETWEEN 01Z-02Z. OTHERWISE A QUIET
NIGHT IS IN STORE FOR AREA TAF SITES.

THE SUNDAY FORECAST IS CHALLENGING AS THERE ARE CHANCES FOR LIGHT
SHRA THROUGH MID AFTERNOON AND THEN CHANCES FOR SHRA/TSRA AFTER
THAT POINT. ONGOING WIDESPREAD STORMS ACROSS THE SOUTHERN PLAINS
ARE LIKELY TO HOLD BACK THE ELEVATED WARM FRONT AND ASSOCIATED
MOISTURE RETURN THROUGH TONIGHT AND EVEN INTO SUNDAY. THIS MAY BE
ENOUGH TO PREVENT MUCH SHOWER COVERAGE IN THE AFTERNOON AND EVEN
THE EVENING. FEEL RFD HAS THE BEST CHANCES FOR GETTING INTO SOME
CONVECTIVE ACTIVITY LATE IN THE DAY AND INTO SUNDAY
EVENING...WHILE AREAWIDE OVERNIGHT SUNDAY. OVERALL CONFIDENCE IS
LOW ON SPECIFIC TIMING AND COVERAGE DURING THE DAY SUNDAY...BUT
HAVE FELT A LITTLE STRONGER LEANING TOWARD THE MAINLY DRY ROUTE
DURING THE DAY FOR CHICAGO AREA TAF SITES.

WINDS ON THE REGIONAL SCALE WILL BECOME SOUTHEAST ON SUNDAY AND
GRADUALLY INCREASE IN SPEED WITH THE PRESSURE GRADIENT. THE
DIRECTION WILL FAVOR A LAKE BREEZE AGAIN IN NORTHEAST
ILLINOIS...WHICH WOULD TURN WINDS MORE DUE EASTERLY IF IT CAN
REACH ORD AND MDW. AT THIS TIME HAVE HELD MORE OF A SOUTHEAST
WIND IN THE TAFS...WHICH SHOULD IN ITSELF BE OVER 10 KT WITH SOME
PERIODIC GUSTS.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH IN EASTERLY WIND SPEEDS DIMINISHING IN SPEED BY 01Z.

* MEDIUM IN WINDS ON SUNDAY AND TIMING OF 10+ KTS.

* HIGH THAT ANY TSRA CHANCES WOULD BE AFTER 21Z ON SUNDAY...BUT
  LOW ON SHRA TIMING AND COVERAGE ON SUNDAY AND SUNDAY EVENING.


//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 232337
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* EASTERLY WINDS AROUND 10 KT THROUGH SUNSET BEFORE DIMINISHING IN
  SPEED AND SLOWLY VEERING.

* SOUTHEAST WINDS INCREASING TO 10 KT+ BY EARLY AFTERNOON SUNDAY.

* CHANCE OF -SHRA MID-LATE SUNDAY MORNING THEN INCREASING CHANCES
  INCLUDING TSRA LATE IN THE DAY AND MORE SO AFTER DARK.


//DISCUSSION...UPDATED 00Z...

THE LAKE BREEZE BOUNDARY WILL CONTINUE TO INCH WESTWARD BEFORE
FADING AROUND OR SOON AFTER SUNDOWN. AS THAT OCCURS...THE EASTERLY
WINDS AT ORD AND MDW WILL EASE IN SPEED AND GRADUALLY VEER. SO 10
KT+ SPEEDS SHOULD BE FADING BETWEEN 01Z-02Z. OTHERWISE A QUIET
NIGHT IS IN STORE FOR AREA TAF SITES.

THE SUNDAY FORECAST IS CHALLENGING AS THERE ARE CHANCES FOR LIGHT
SHRA THROUGH MID AFTERNOON AND THEN CHANCES FOR SHRA/TSRA AFTER
THAT POINT. ONGOING WIDESPREAD STORMS ACROSS THE SOUTHERN PLAINS
ARE LIKELY TO HOLD BACK THE ELEVATED WARM FRONT AND ASSOCIATED
MOISTURE RETURN THROUGH TONIGHT AND EVEN INTO SUNDAY. THIS MAY BE
ENOUGH TO PREVENT MUCH SHOWER COVERAGE IN THE AFTERNOON AND EVEN
THE EVENING. FEEL RFD HAS THE BEST CHANCES FOR GETTING INTO SOME
CONVECTIVE ACTIVITY LATE IN THE DAY AND INTO SUNDAY
EVENING...WHILE AREAWIDE OVERNIGHT SUNDAY. OVERALL CONFIDENCE IS
LOW ON SPECIFIC TIMING AND COVERAGE DURING THE DAY SUNDAY...BUT
HAVE FELT A LITTLE STRONGER LEANING TOWARD THE MAINLY DRY ROUTE
DURING THE DAY FOR CHICAGO AREA TAF SITES.

WINDS ON THE REGIONAL SCALE WILL BECOME SOUTHEAST ON SUNDAY AND
GRADUALLY INCREASE IN SPEED WITH THE PRESSURE GRADIENT. THE
DIRECTION WILL FAVOR A LAKE BREEZE AGAIN IN NORTHEAST
ILLINOIS...WHICH WOULD TURN WINDS MORE DUE EASTERLY IF IT CAN
REACH ORD AND MDW. AT THIS TIME HAVE HELD MORE OF A SOUTHEAST
WIND IN THE TAFS...WHICH SHOULD IN ITSELF BE OVER 10 KT WITH SOME
PERIODIC GUSTS.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH IN EASTERLY WIND SPEEDS DIMINISHING IN SPEED BY 01Z.

* MEDIUM IN WINDS ON SUNDAY AND TIMING OF 10+ KTS.

* HIGH THAT ANY TSRA CHANCES WOULD BE AFTER 21Z ON SUNDAY...BUT
  LOW ON SHRA TIMING AND COVERAGE ON SUNDAY AND SUNDAY EVENING.


//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 232337
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* EASTERLY WINDS AROUND 10 KT THROUGH SUNSET BEFORE DIMINISHING IN
  SPEED AND SLOWLY VEERING.

* SOUTHEAST WINDS INCREASING TO 10 KT+ BY EARLY AFTERNOON SUNDAY.

* CHANCE OF -SHRA MID-LATE SUNDAY MORNING THEN INCREASING CHANCES
  INCLUDING TSRA LATE IN THE DAY AND MORE SO AFTER DARK.


//DISCUSSION...UPDATED 00Z...

THE LAKE BREEZE BOUNDARY WILL CONTINUE TO INCH WESTWARD BEFORE
FADING AROUND OR SOON AFTER SUNDOWN. AS THAT OCCURS...THE EASTERLY
WINDS AT ORD AND MDW WILL EASE IN SPEED AND GRADUALLY VEER. SO 10
KT+ SPEEDS SHOULD BE FADING BETWEEN 01Z-02Z. OTHERWISE A QUIET
NIGHT IS IN STORE FOR AREA TAF SITES.

THE SUNDAY FORECAST IS CHALLENGING AS THERE ARE CHANCES FOR LIGHT
SHRA THROUGH MID AFTERNOON AND THEN CHANCES FOR SHRA/TSRA AFTER
THAT POINT. ONGOING WIDESPREAD STORMS ACROSS THE SOUTHERN PLAINS
ARE LIKELY TO HOLD BACK THE ELEVATED WARM FRONT AND ASSOCIATED
MOISTURE RETURN THROUGH TONIGHT AND EVEN INTO SUNDAY. THIS MAY BE
ENOUGH TO PREVENT MUCH SHOWER COVERAGE IN THE AFTERNOON AND EVEN
THE EVENING. FEEL RFD HAS THE BEST CHANCES FOR GETTING INTO SOME
CONVECTIVE ACTIVITY LATE IN THE DAY AND INTO SUNDAY
EVENING...WHILE AREAWIDE OVERNIGHT SUNDAY. OVERALL CONFIDENCE IS
LOW ON SPECIFIC TIMING AND COVERAGE DURING THE DAY SUNDAY...BUT
HAVE FELT A LITTLE STRONGER LEANING TOWARD THE MAINLY DRY ROUTE
DURING THE DAY FOR CHICAGO AREA TAF SITES.

WINDS ON THE REGIONAL SCALE WILL BECOME SOUTHEAST ON SUNDAY AND
GRADUALLY INCREASE IN SPEED WITH THE PRESSURE GRADIENT. THE
DIRECTION WILL FAVOR A LAKE BREEZE AGAIN IN NORTHEAST
ILLINOIS...WHICH WOULD TURN WINDS MORE DUE EASTERLY IF IT CAN
REACH ORD AND MDW. AT THIS TIME HAVE HELD MORE OF A SOUTHEAST
WIND IN THE TAFS...WHICH SHOULD IN ITSELF BE OVER 10 KT WITH SOME
PERIODIC GUSTS.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH IN EASTERLY WIND SPEEDS DIMINISHING IN SPEED BY 01Z.

* MEDIUM IN WINDS ON SUNDAY AND TIMING OF 10+ KTS.

* HIGH THAT ANY TSRA CHANCES WOULD BE AFTER 21Z ON SUNDAY...BUT
  LOW ON SHRA TIMING AND COVERAGE ON SUNDAY AND SUNDAY EVENING.


//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 232202
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
502 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* LAKE BREEZE LIKELY REACHING MIDWAY BY 23Z...POSSIBLY REACHING
  ORD AFTER 2330Z
* POSSIBLE LIGHT SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

MTF/KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM-HIGH ON LAKE BREEZE REACHING MDW AND TIMING. LOW IN IF
  LAKE BREEZE WILL REACH ORD
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN
  IT WILL OCCUR AT THE TERMINAL SUNDAY PM

MTF/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 232202
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
502 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* LAKE BREEZE LIKELY REACHING MIDWAY BY 23Z...POSSIBLY REACHING
  ORD AFTER 2330Z
* POSSIBLE LIGHT SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

MTF/KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM-HIGH ON LAKE BREEZE REACHING MDW AND TIMING. LOW IN IF
  LAKE BREEZE WILL REACH ORD
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN
  IT WILL OCCUR AT THE TERMINAL SUNDAY PM

MTF/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 232202
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
502 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* LAKE BREEZE LIKELY REACHING MIDWAY BY 23Z...POSSIBLY REACHING
  ORD AFTER 2330Z
* POSSIBLE LIGHT SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

MTF/KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM-HIGH ON LAKE BREEZE REACHING MDW AND TIMING. LOW IN IF
  LAKE BREEZE WILL REACH ORD
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN
  IT WILL OCCUR AT THE TERMINAL SUNDAY PM

MTF/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 232202
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
502 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* LAKE BREEZE LIKELY REACHING MIDWAY BY 23Z...POSSIBLY REACHING
  ORD AFTER 2330Z
* POSSIBLE LIGHT SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

MTF/KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM-HIGH ON LAKE BREEZE REACHING MDW AND TIMING. LOW IN IF
  LAKE BREEZE WILL REACH ORD
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN
  IT WILL OCCUR AT THE TERMINAL SUNDAY PM

MTF/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON/EARLY
  EVENING...THOUGH VARIABLE FOR A TIME TODAY.
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 231940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 PM CDT SAT MAY 23 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON/EARLY
  EVENING...THOUGH VARIABLE FOR A TIME TODAY.
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231924
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
224 PM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON/EARLY
  EVENING...THOUGH VARIABLE FOR A TIME TODAY.
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231924
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
224 PM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON/EARLY
  EVENING...THOUGH VARIABLE FOR A TIME TODAY.
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 231924
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
224 PM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON/EARLY
  EVENING...THOUGH VARIABLE FOR A TIME TODAY.
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231924
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
224 PM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON/EARLY
  EVENING...THOUGH VARIABLE FOR A TIME TODAY.
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 231804
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
104 PM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 231804
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
104 PM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* SW WINDS BACKING TO SE LATE THIS AFTERNOON
* SHOWERS LATE TONIGHT INTO EARLY SUNDAY
* ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDER PSBL SUNDAY AFTN

KMD

//DISCUSSION...UPDATED 18Z...

THE BATTLE OF THE LAKE INFLUENCE AND WARM SYNOPTIC SOUTHERLY FLOW
IS PLAYING OUT WITH THE ORD AND MDW ON THE BORDER OF THESE TWO
VARYING INFLUENCES ON WINDS. AN EARLIER LAKE BREEZE HAS STALLED
OUT CLOSER TO I-94 AND MAKING LITTLE PROGRESS AT THIS TIME. WINDS
ARE GENERALLY SSW ON THE WEST SIDE OF THE LAKE BREEZE AND ANYWHERE
FROM NE TO SE BEHIND IT. VARIABLE WINDS HAVE RESULTED AT TIMES
WITH THIS. GENERALLY EXPECT THAT WESTERN TAF SITES WILL HOLD THE
SSW WINDS THROUGH THE AFTERNOON WITH THE SE WINDS TAKING MORE
CONTROL FROM ORD EASTWARD LATE THIS AFTERNOON AND EVENING...THOUGH
TIMING ON THIS REMAINS A CHALLENGE. ALSO...WINDS BEHIND THE LAKE
BREEZE ARE NOT VERY STRONG...SO IT SHOULD BE LOW OPERATIONAL
IMPACT.

ATTENTION TURNS TO SHOWER/THUNDER POTENTIAL SUNDAY. THE LEADING
EDGE OF LOW LEVEL WARM AIR SURGES NORTHWARD LATE TONIGHT...AND
ALONG THIS BOUNDARY SOME SHOWERS ARE EXPECTED IN THE 10Z-15Z TIME
FRAME SOUTH TO NORTH. COVERAGE WILL NOT BE WIDESPREAD...THUS THE
VCSH MENTION. THEN AFTER A LULL...EXPECT THAT AS LOW LEVEL
MOISTURE ADVECTION INCREASES ANOTHER ROUND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS CAN BE EXPECTED SUNDAY AFTERNOON. THOUGH
CONFIDENCE IS HIGH IN A PERIOD OF SHOWERS AND THUNDERSTORMS GUIDANCE
VARIES WITH WHETHER THIS BEGINS AT 18Z OR HOLDS OFF UNTIL CLOSER
TO 0Z THUS HAVE CARRIED A -SHRA MENTION IN THE ORD 30 HR TAF FOR
NOW TO ACCOUNT FOR UNCERTAINTY IN TIMING.

KMD


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM ON WIND SPEED AND DIRECTION.
* MEDIUM ON SHOWER POTENTIAL AND TIMING IN THE TAFS
* HIGH IN NO THUNDER UNTIL SUNDAY AFTERNOON...BUT LOW ON IF/WHEN IT
  WILL OCCUR AT THE TERMINAL SUNDAY PM.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1105 AM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* POTENTIAL LAKE BREEZE TURNING SE WINDS MORE EASTERLY BY 20Z AND
  INCREASING TO 10-12KT WITH AN OCNL HIGHER GUST.

* SHOWERS LATE SUNDAY MORNING

KREIN/KMD

//DISCUSSION...UPDATED 16Z...

SUBTLE LAKE BREEZE SEEN ON TORD REFLECTIVITY AND NEAR LAKE MESONET
OBS SHOWING WINDS SHIFTING TO ENE BUT FAIRLY LIGHT. EXPECT THAT
THERE WILL BE SOME SHIFTING WINDS TO MORE ESE THROUGH THE DAY BUT
CONFIDENCE ON TIMING IS LOW AS THE SETUP SUGGESTS THE LAKE BREEZE
REMAINING SOMEWHAT AT BAY GIVEN THE SYNOPTIC SOUTHERLY WINDS IN
PLACE. SOME HI RES GUIDANCE DOES PUSH THE LAKE BREEZE THROUGH ORD
AND MDW LATE IN THE DAY WITH MORE OF AN EASTERLY COMPONENT SO WILL
NEED TO MONITOR TRENDS.

KMD

PREVIOUS DISCUSSION FROM 12Z...

HIGH PRESSURE IS CENTERED OVER THE MID ATLANTIC REGION THIS
MORNING. AS THE HIGH SHIFTS GRADUALLY TO THE EAST AND SOUTH
LOW PRESSURE DEEPENS IN THE LEE OF THE ROCKIES...THE LARGE SCALE
PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN. SOUTHERLY WINDS
WILL STRENGTHEN THROUGH THE MORNING WITH SPEEDS INCREASING TO
ARND 10KT BY LATE MORNING. A LAKE BREEZE SHOULD DEVELOP ALONG THE
NORTHEAST ILLINOIS LAKEFRONT AND SLOWLY MOVE INLAND. THE LATEST
HIGH RES MODEL GUIDANCE SUGGESTS THAT THE LAKE BREEZE SHOULD PUSH
WEST OF ORD AND MDW...TURNING WINDS BACK TO SELY AND INCREASING
SLIGHTLY TO 11-12KT WITH OCNL HIGHER GUSTS.

MOISTURE WILL CONTINUE TO INCREASE ALOFT AND LEAD TO THE MID AND
HIGH LEVEL CLOUDS LOWERING TO 5000-8000 FT DURING SATURDAY...WITH
RAIN POSSIBLE BY THE PRE-DAWN HOURS AT RFD AND BY LATE MORNING
INVOF ORD.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM IN THE TIMING OF THE LAKE BREEZE AND THE SPEED/DIRECTION
  FOLLOWING LAKE BREEZE PASSAGE.

* LOW/MEDIUM THAT ORD/MDW SEE PRECIP SUNDAY MORNING...BUT HIGH
  FOR NO THUNDER.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1105 AM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* POTENTIAL LAKE BREEZE TURNING SE WINDS MORE EASTERLY BY 20Z AND
  INCREASING TO 10-12KT WITH AN OCNL HIGHER GUST.

* SHOWERS LATE SUNDAY MORNING

KREIN/KMD

//DISCUSSION...UPDATED 16Z...

SUBTLE LAKE BREEZE SEEN ON TORD REFLECTIVITY AND NEAR LAKE MESONET
OBS SHOWING WINDS SHIFTING TO ENE BUT FAIRLY LIGHT. EXPECT THAT
THERE WILL BE SOME SHIFTING WINDS TO MORE ESE THROUGH THE DAY BUT
CONFIDENCE ON TIMING IS LOW AS THE SETUP SUGGESTS THE LAKE BREEZE
REMAINING SOMEWHAT AT BAY GIVEN THE SYNOPTIC SOUTHERLY WINDS IN
PLACE. SOME HI RES GUIDANCE DOES PUSH THE LAKE BREEZE THROUGH ORD
AND MDW LATE IN THE DAY WITH MORE OF AN EASTERLY COMPONENT SO WILL
NEED TO MONITOR TRENDS.

KMD

PREVIOUS DISCUSSION FROM 12Z...

HIGH PRESSURE IS CENTERED OVER THE MID ATLANTIC REGION THIS
MORNING. AS THE HIGH SHIFTS GRADUALLY TO THE EAST AND SOUTH
LOW PRESSURE DEEPENS IN THE LEE OF THE ROCKIES...THE LARGE SCALE
PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN. SOUTHERLY WINDS
WILL STRENGTHEN THROUGH THE MORNING WITH SPEEDS INCREASING TO
ARND 10KT BY LATE MORNING. A LAKE BREEZE SHOULD DEVELOP ALONG THE
NORTHEAST ILLINOIS LAKEFRONT AND SLOWLY MOVE INLAND. THE LATEST
HIGH RES MODEL GUIDANCE SUGGESTS THAT THE LAKE BREEZE SHOULD PUSH
WEST OF ORD AND MDW...TURNING WINDS BACK TO SELY AND INCREASING
SLIGHTLY TO 11-12KT WITH OCNL HIGHER GUSTS.

MOISTURE WILL CONTINUE TO INCREASE ALOFT AND LEAD TO THE MID AND
HIGH LEVEL CLOUDS LOWERING TO 5000-8000 FT DURING SATURDAY...WITH
RAIN POSSIBLE BY THE PRE-DAWN HOURS AT RFD AND BY LATE MORNING
INVOF ORD.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM IN THE TIMING OF THE LAKE BREEZE AND THE SPEED/DIRECTION
  FOLLOWING LAKE BREEZE PASSAGE.

* LOW/MEDIUM THAT ORD/MDW SEE PRECIP SUNDAY MORNING...BUT HIGH
  FOR NO THUNDER.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 231437
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
937 AM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL LAKE BREEZE TURNING SE WINDS MORE EASTERLY BY 20Z AND
  INCREASING TO 10-12KT WITH AN OCNL HIGHER GUST.

* SHOWERS LATE SUNDAY MORNING

KREIN/KMD

//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE IS CENTERED OVER THE MID ATLANTIC REGION THIS
MORNING. AS THE HIGH SHIFTS GRADUALLY TO THE EAST AND SOUTH
LOW PRESSURE DEEPENS IN THE LEE OF THE ROCKIES...THE LARGE SCALE
PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN. SOUTHERLY WINDS
WILL STRENGTHEN THROUGH THE MORNING WITH SPEEDS INCREASING TO
ARND 10KT BY LATE MORNING. A LAKE BREEZE SHOULD DEVELOP ALONG THE
NORTHEAST ILLINOIS LAKEFRONT AND SLOWLY MOVE INLAND. THE LATEST
HIGH RES MODEL GUIDANCE SUGGESTS THAT THE LAKE BREEZE SHOULD PUSH
WEST OF ORD AND MDW...TURNING WINDS BACK TO SELY AND INCREASING
SLIGHTLY TO 11-12KT WITH OCNL HIGHER GUSTS.

MOISTURE WILL CONTINUE TO INCREASE ALOFT AND LEAD TO THE MID AND
HIGH LEVEL CLOUDS LOWERING TO 5000-8000 FT DURING SATURDAY...WITH
RAIN POSSIBLE BY THE PRE-DAWN HOURS AT RFD AND BY LATE MORNING
INVOF ORD.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM IN THE TIMING OF THE LAKE BREEZE AND THE SPEED/DIRECTION
  FOLLOWING LAKE BREEZE PASSAGE.

* LOW THAT ORD/MDW SEE PRECIP SUNDAY MORNING...BUT HIGH FOR NO
  THUNDER.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 231437
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
937 AM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL LAKE BREEZE TURNING SE WINDS MORE EASTERLY BY 20Z AND
  INCREASING TO 10-12KT WITH AN OCNL HIGHER GUST.

* SHOWERS LATE SUNDAY MORNING

KREIN/KMD

//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE IS CENTERED OVER THE MID ATLANTIC REGION THIS
MORNING. AS THE HIGH SHIFTS GRADUALLY TO THE EAST AND SOUTH
LOW PRESSURE DEEPENS IN THE LEE OF THE ROCKIES...THE LARGE SCALE
PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN. SOUTHERLY WINDS
WILL STRENGTHEN THROUGH THE MORNING WITH SPEEDS INCREASING TO
ARND 10KT BY LATE MORNING. A LAKE BREEZE SHOULD DEVELOP ALONG THE
NORTHEAST ILLINOIS LAKEFRONT AND SLOWLY MOVE INLAND. THE LATEST
HIGH RES MODEL GUIDANCE SUGGESTS THAT THE LAKE BREEZE SHOULD PUSH
WEST OF ORD AND MDW...TURNING WINDS BACK TO SELY AND INCREASING
SLIGHTLY TO 11-12KT WITH OCNL HIGHER GUSTS.

MOISTURE WILL CONTINUE TO INCREASE ALOFT AND LEAD TO THE MID AND
HIGH LEVEL CLOUDS LOWERING TO 5000-8000 FT DURING SATURDAY...WITH
RAIN POSSIBLE BY THE PRE-DAWN HOURS AT RFD AND BY LATE MORNING
INVOF ORD.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM IN THE TIMING OF THE LAKE BREEZE AND THE SPEED/DIRECTION
  FOLLOWING LAKE BREEZE PASSAGE.

* LOW THAT ORD/MDW SEE PRECIP SUNDAY MORNING...BUT HIGH FOR NO
  THUNDER.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 231137
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 AM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER THE PREVAILING SOUTHERLY
FLOW...ESPECIALLY LOCATIONS OVER NERN IL WHICH WERE IMPACTED BY THE
LAKE BREEZE THAT HAD PUSHED PRETTY MUCH THROUGH ALL OF NERN IL AND
NWRN IN BY EARLY LAST EVENING.  SO...WITH THE EXCEPTION OF THE SMALL
AREA OF FAR NERN IL REMAINING COOLED BY THE LAKE BREEZE...THE HIGHS
IN THE MIDDLE TO UPPER 70S ARE EXPECTED TODAY.  CONDITIONS ARE
EXPECTED TO REMAIN DRY THROUGH THE DAY...THOUGH THICKENING MID AND
HIGH CLOUDINESS IS EXPECTED WITH CLOUD BASES GRADUALLY LOWERING
THROUGH THE DAY AND INTO TONIGHT AS DEEP LAYER MOISTURE INCREASES IN
ADVANCE OF THE SYSTEM DEVELOPING OVER THE WESTERN PLAINS.

BY LATE THIS EVENING...THE SOUTHERN STREAM JET WILL TAKE A TO THE
NORTHEAST AS UPPER RIDGING BUILDS FROM THE SERN CONUS BACK THROUGH
THE UPPER MISSISSIPPI VALLEY.  THIS WILL SHUNT THE DEEP LAYER
MOISTURE TRANSPORT ON A MORE NORTHEASTERLY TRAJECTORY FROM THE WRN
GULFMEX AND TX INTO THE MIDDLE MISSISSIPPI VALLEY.  THIS WILL BE THE
SOURCE MOISTURE FOR INCREASING PRECIPITATION CHANCES GOING INTO
EARLY SUNDAY MORNING.  THE INITIAL PCPN CHANCES SHOULD BEGIN WEST OF
THE I-39 CORRIDOR AFTER MIDNIGHT TONIGHT AND INTO THE EARLY MORNING
HOURS.  THERE COULD BE A FEW TSRA WITH THIS INITIAL PCPN...BUT
GENERALLY...SHOWERS ARE MORE LIKELY...WITH THE INCREASING TS CHANCES
INTO THE DAY ON SUNDAY.  INCREASING AND THICKENING CLOUD COVER ALONG
WITH DEWPOINTS RISING BACK INTO THE 50S OVERNIGHT TONIGHT INTO
SUNDAY MORNING...OVERNIGHT LOW TEMPS WILL BE A BIT MORE
SEASONABLE...WITH LOWS IN THE LOWER 50S...EXPECT THE WAUKEEGAN AREA
WHICH COULD STILL BE UNDER THE INFLUENCE OF LAKE-COOLED AIR...WITH
LOWS IN THE UPPER 40S.

KREIN

&&

.LONG TERM...
253 AM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MEMORIAL DAY...
MAIN CONCERN FOR THE SECOND HALF OF THE HOLIDAY WEEKEND WILL BE
PRECIP CHANCES/TIMING/COVERAGE. 500MB HEIGHTS WILL NUDGE UP A LITTLE
SUN...WHICH LIKELY WILL SIGNAL A DELAY IN THE ONSET OF PRECIP FOR
THE BULK OF THE FORECAST AREA. FURTHER WEST ACROSS THE CENTRAL
CONUS...HEIGHT FALLS WILL BE NOTED WITH AN ATMOSPHERIC PLUME OF
MOISTURE STREAMING NORTH FROM THE WESTERN GULF ALONG RETURN FLOW
MOISTURE FROM THE DOWNSTREAM SFC RIDGE. GUIDANCE HAS BECOME LESS
ORGANIZED WITH THE SFC WAVE AND SHIFTED FURTHER WEST ACROSS THE
FRONT RANGE OF THE ROCKIES MIDDAY SUN...ALL POINTING TOWARDS
DELAYING THE PRECIP UNTIL MAINLY LATE AFTN AND POSSIBLY MORE TOWARDS
THE LATE EVENING HOURS. 500MB TROUGH WILL BE DRIFTING EAST/NORTHEAST
SUN EVE/EARLY MON...WITH HEIGHT FALLS BEGINNING TO OCCUR OVER THE
BULK OF THE FORECAST AREA.

THIS COUPLED WITH AN ANOMALOUSLY STRONG LVLL NOCTURNAL 40KT JET AND
THE SOUTHERLY WIND COMPONENT PROGGED AT NEARLY 4 SIGMA...SIGNALS
THAT OVERNIGHT SUN/EARLY MON IF AN ATMOSPHERIC WAVE CAN DEVELOP IT
WOULD LIKELY TRIGGER SOME BRIEF DOWNPOURS IN THIS TIMEFRAME. HOWEVER
THE SFC FEATURES CONTINUE TO BE LACKING IN ORGANIZATION...BUT WILL
MAINTAIN LIKELY POPS THRU DAYBREAK MON GIVEN THE PATTERN SETUP. BUT
COULD SEE THIS BEING LESS COVERAGE AND POSSIBLY ONLY EMBEDDED
THUNDER. SFC MOISTURE WILL STILL BE FELT AS DEW POINTS IN THE
LOW/MID 60S WILL ADVECT NORTH ACROSS THE REGION. AFTN TEMPS WILL BE
SLIGHTLY DIFFICULT GIVEN THE HIGH WATER CONTENT WITHIN
PARCELS...HOWEVER GUIDANCE HAS MAINTAINED A HIGH CONFIDENCE IN TEMPS
PUSHING THE UPR 70S TO ARND 80 BOTH SUN/MON.

LLVL JET WILL BEGIN TO PEEL NORTH/NORTHEAST OF THE REGION MON...WITH
A PROGGED DRY WEDGE LIFTING NORTHEAST ACROSS THE CENTRAL CONUS
TOWARDS THE FORECAST AREA BY MIDDAY MON. HAVE REFLECTED THIS WITH
SLIGHTLY LESS POPS IN THE MON AFTN TIMEFRAME...AND COULD SEE THE
AFTN/EVE HOURS END UP BEING DRY. ENSEMBLES ARE CURRENTLY INDICATING
LESS CONFIDENCE IN PRECIP IN THE EVENING HOURS...SO THE LATER
FORECASTS MAY INDEED FURTHER TRIM POPS FOR MON AFTN/EVE.

TUESDAY THROUGH FRIDAY... 500MB TROUGH WILL CONTINUE TO DRIFT EAST
TUE...WITH THE AXIS PIVOTING OVER THE CENTRAL CONUS. THIS WILL ALLOW
HEIGHTS TO FALL SLIGHTLY WITH MOIST SOUTHERLY CONTINUING ACROSS THE
REGION THROUGH THE MIDDLE OF NEXT WEEK. HIGH AMPLITUDE RIDGING
REMAINS ACROSS WESTERN CANADA WITH DOWNSTREAM RIDGING DEVELOPING
OVER THE SOUTHEAST CONUS. THIS WILL ALLOW A PERSISTENT SOUTHWEST
FLOW FOR THE SECOND HALF OF NEXT WEEK...WITH PERIODIC CHANCES FOR
SHOWERS AND THUNDERSTORMS.

TEMPERATURES WILL GENERALLY BE IN THE 70S WITH A FEW AFTERNOONS
TOUCHING 80 DEGREES NEXT WEEK. WITH GENERALLY AN OFFSHORE FLOW
EXPECTED FOR THE BULK OF THE EXTENDED...AREAS ADJACENT TO LAKE
MICHIGAN WILL BE ABLE TO MAINTAIN THE WARMTH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* POTENTIAL LAKE BREEZE TURNING WINDS SOUTHEASTERLY BY 20Z AND
  INCREASING TO 10-12KT WITH AN OCNL HIGHER GUST.

KREIN

//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE IS CENTERED OVER THE MID ATLANTIC REGION THIS
MORNING. AS THE HIGH SHIFTS GRADUALLY TO THE EAST AND SOUTH
LOW PRESSURE DEEPENS IN THE LEE OF THE ROCKIES...THE LARGE SCALE
PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN. SOUTHERLY WINDS
WILL STRENGTHEN THROUGH THE MORNING WITH SPEEDS INCREASING TO
ARND 10KT BY LATE MORNING. A LAKE BREEZE SHOULD DEVELOP ALONG THE
NORTHEAST ILLINOIS LAKEFRONT AND SLOWLY MOVE INLAND. THE LATEST
HIGH RES MODEL GUIDANCE SUGGESTS THAT THE LAKE BREEZE SHOULD PUSH
WEST OF ORD AND MDW...TURNING WINDS BACK TO SELY AND INCREASING
SLIGHTLY TO 11-12KT WITH OCNL HIGHER GUSTS.

MOISTURE WILL CONTINUE TO INCREASE ALOFT AND LEAD TO THE MID AND
HIGH LEVEL CLOUDS LOWERING TO 5000-8000 FT DURING SATURDAY...WITH
RAIN POSSIBLE BY THE PRE-DAWN HOURS AT RFD AND BY LATE MORNING
INVOF ORD.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN WINDS THROUGH MIDDAY SATURDAY.

* MEDIUM CONFIDENCE IN THE TIMING OF THE LAKE BREEZE AND THE
  SPEED/DIRECTION FOLLOWING LAKE BREEZE PASSAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...CHANCE OF SHRA/TSRA. SOUTH-SOUTHEAST WINDS.

MONDAY...PERIODS OF SHRA/TSRA. GUSTY SOUTHWEST WINDS.

TUESDAY - THURSDAY...PERIODIC CHANCES FOR SHRA/TSRA. SOUTHWEST
WINDS.

FRIDAY...CHANCES OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
305 AM CDT

SURFACE HIGH PRESSURE HAS BECOME CENTERED OVER THE EASTERN GREAT
LAKES WITH A LIGHT GRADIENT OVER LAKE MICHIGAN EARLY THIS MORNING.
WINDS ARE GENERALLY SOUTHERLY. LOW PRESSURE WILL REMAIN WELL
SOUTHWEST OF THE REGION OVER THE CENTRAL ROCKIES THIS
AFTERNOON...HOWEVER THE GRADIENT IS POISED TO TIGHTEN SLIGHTLY
THIS EVENING AND ALLOW WAVES TO BUILD ACROSS THE NORTHERN PORTIONS
OF THE LAKE. WITH WARM/MOIST AIR LIFTING NORTH OVER THE LAKE FOR
THE SECOND HALF OF THE WEEKEND...THE SETUP APPEARS FAVORABLE FOR
FOG DEVELOPMENT. IT IS POSSIBLE SOME POCKETS OF DENSE FOG MAY
DEVELOP AT SOME POINT THIS HOLIDAY WEEKEND.

AS THE LOW PRESSURE BEGINS TO LIFT NORTHEAST INTO THE CENTRAL
PLAINS LATE SUN INTO EARLY MON...THIS WILL PUSH A SLIGHTLY TIGHTER
GRADIENT OVER THE SOUTHERN HALF OF LAKE MICHIGAN MON. AS A RESULT
WINDS MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS MON.

THROUGH NEXT WEEK WINDS WILL REMAIN SOUTHERLY OVER THE LAKE...WITH
CONTINUED PERIODS OF FOG EXPECTED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KLOT 231137
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 AM CDT SAT MAY 23 2015

.SHORT TERM...
251 AM CDT

SATURDAY AND SATURDAY NIGHT...

SATURDAY IS SHAPING UP TO BE A RELATIVELY QUIET DAY.  WITH HIGH
PRESSURE OVER THE EASTERN GREAT LAKES GRADUALLY SLIDING SOUTHEAST
OFF THE MID ATLANTIC COAST AND LEE CYCLOGENESIS OVER THE WESTERN
PLAINS...WINDS WILL...SYNOPTICALLY...VEER FROM EASTERLY TO SOUTHERLY
THROUGH THE DAY TODAY.  HOWEVER...BY THIS AFTERNOON...SFC RIDGING
EXTENDING FROM THE HIGH CENTER THROUGH THE UPPER MISSISSIPPI VALLEY
WILL SET UP A WEAK SOUTHERLY PRESSURE GRADIENT OVER THE REGION.
SO...WHILE THE SYNOPTIC WINDS SHOULD REMAIN SOUTHERLY AROUND 10KT
THROUGH THE DAY...SOME LAKE INFLUENCE SHOULD SET UP A LAKE BREEZE.
UNDER THE EXPECTED SFC PATTERN...A NW-SE ORIENTED BOUNDARY IS
EXPECTED TO SET PUSH...PUSHING INLAND INTO LAKE COUNTY...KEEPING THE
WAUKEEGAN AREA ON THE COOLER SIDE.  THERE IS SOME QUESTION AS TO HOW
FAR INLAND THE LAKE BREEZE WILL PUSH INTO COOK COUNTY...BUT THE
LATEST HIGH RES SFC WIND GUIDANCE DOES SUGGEST THAT THE LAKE BREEZE
COULD PUSH AS FAR WEST AS ORD...SO...HAVE KEPT MAX TEMPS OVER ERN
COOK AND LAKE COUNTIES...INCLUDING DOWNTOWN CHICAGO ONLY IN THE
LOWER 60S.  THE REMAINDER OF THE AREA SHOULD SEE TEMPERATURES A BIT
HIGHER THAN YESTERDAY UNDER T