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000
FXUS63 KILX 301552
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1052 AM CDT Sat Aug 30 2014

.UPDATE...
ISSUED AT 1052 AM CDT SAT AUG 30 2014

Much of central Illinois remains convection-free this morning,
except for the far SE KILX CWA south of I-70 where showers and
thunderstorms are ongoing. 15z/10am visible satellite imagery is
beginning to show an enhanced band of Cu along the Illinois River
that will eventually become a broken line of thunderstorms this
afternoon. HRRR shows storms developing along the I-55 corridor
after 20z, so have adjusted PoPs accordingly. Have focused likely
PoPs along/east of I-55 by mid-afternoon into the early evening
hours. Further west, will only carry low chances along/west of the
Illinois River this afternoon, then dry by evening.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 658 AM CDT SAT AUG 30 2014

Scattered showers continue this morning mainly east of KDEC and
could produce isolated MVFR cig/vsby. As daytime heating
begins...expecting intensification of thunderstorm activity.
Location/timing of thunderstorms still uncertain at this time so
have limited mention to VCTS after 16Z-18Z. After 00Z...drying
conditions expected to begin spreading eastward across Illinois.
Western TAF sites KPIA-KSPI likely to see fog formation overnight
while eastern TAF sites KDEC-KCMI could see continued showers
overnight until around 12Z and have left VCSH in forecast.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...07
AVIATION...ONTON





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000
FXUS63 KLOT 301422
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
922 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

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

* TOUGH DECISIONS REGARDING TSRA TRENDS...TIMING...AND COVERAGE.
  DRY TAF AT ORD/MDW REFLECTS BELIEF THAT FOCUS WILL SHIFT JUST
  SOUTH AND EAST OF TERMINALS AS CHANCES INCREASE. BUT VCTS OR
  TEMPO TSRA MAY NEED TO BE REINTRODUCED. FELT A FULL DAY OF VCTS
  WOULD NOT BE HELPFUL.

LENNING

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

SCT SHRA AND ISOLD TSRA CONTINUE THROUGH THE DAY TODAY AS THE AREA
REMAINS ENTRENCHED IN A WARM/MOIST AIRMASS. A WEAK COLD FRONT IS
EXPECTED TO MOVE ACROSS THE AREA TODAY IN ASSOCIATION WITH A
STRONGER UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD
PROVIDE SOME FOCUS FOR MORE THUNDERSTORM ACTIVITY. HOWEVER...THE
TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN THE TS
COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A TIME
BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL GUIDANCE
SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT MOVES
THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON HOURS.
HAVE OPTED TO GO WITH THE TEMPO GROUP FOR TS FOR THE MOST
FAVORABLE TIME FOR CONVECTIVE ACTIVITY OVER THE AREA...BUT THIS IS
STILL A LOW CONFIDENCE FORECAST.

WINDS SHOULD BECOME MORE SWLY WITH GUSTS TO 15-20KT FOR THE LATE
MORNING INTO EARLY EVENING AS SOME BREAKS IN THE OVERCAST ALLOWS
FOR SOME MIXING DOWN OF STRONGER WINDS ALOFT. WINDS SHOULD DROP
OFF AND BECOME LGT/VRBL OVERNIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA. WITH CLEARING SKIES...LIGHT WINDS AND AMPLE RESIDUAL LOW
LEVEL MOISTURE IN PLACE...THERE IS AN INCREASING CHANCE FOR FOG
AND STATUS TO DEVELOP DURG THE LATE NIGHT HOURS TONIGHT.

KREIN

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

* LOW TO MEDIUM REGARDING CONVECTIVE TRENDS.

* MEDIUM TO HIGH REGARDING SOUTHWEST WINDS EXCEPT NEAR TSRA.

LENNING

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

SUNDAY NIGHT...VFR.

MONDAY...PERIODS OF TSRA LIKELY.

TUESDAY...SLIGHT CHANCE TSRA EARLY.

WEDNESDAY...SLIGHT CHANCE TSRA OVERNIGHT.

THURSDAY AND FRIDAY...CHANCE TSRA.

KREIN

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 301422
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
922 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

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

* TOUGH DECISIONS REGARDING TSRA TRENDS...TIMING...AND COVERAGE.
  DRY TAF AT ORD/MDW REFLECTS BELIEF THAT FOCUS WILL SHIFT JUST
  SOUTH AND EAST OF TERMINALS AS CHANCES INCREASE. BUT VCTS OR
  TEMPO TSRA MAY NEED TO BE REINTRODUCED. FELT A FULL DAY OF VCTS
  WOULD NOT BE HELPFUL.

LENNING

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

SCT SHRA AND ISOLD TSRA CONTINUE THROUGH THE DAY TODAY AS THE AREA
REMAINS ENTRENCHED IN A WARM/MOIST AIRMASS. A WEAK COLD FRONT IS
EXPECTED TO MOVE ACROSS THE AREA TODAY IN ASSOCIATION WITH A
STRONGER UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD
PROVIDE SOME FOCUS FOR MORE THUNDERSTORM ACTIVITY. HOWEVER...THE
TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN THE TS
COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A TIME
BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL GUIDANCE
SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT MOVES
THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON HOURS.
HAVE OPTED TO GO WITH THE TEMPO GROUP FOR TS FOR THE MOST
FAVORABLE TIME FOR CONVECTIVE ACTIVITY OVER THE AREA...BUT THIS IS
STILL A LOW CONFIDENCE FORECAST.

WINDS SHOULD BECOME MORE SWLY WITH GUSTS TO 15-20KT FOR THE LATE
MORNING INTO EARLY EVENING AS SOME BREAKS IN THE OVERCAST ALLOWS
FOR SOME MIXING DOWN OF STRONGER WINDS ALOFT. WINDS SHOULD DROP
OFF AND BECOME LGT/VRBL OVERNIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA. WITH CLEARING SKIES...LIGHT WINDS AND AMPLE RESIDUAL LOW
LEVEL MOISTURE IN PLACE...THERE IS AN INCREASING CHANCE FOR FOG
AND STATUS TO DEVELOP DURG THE LATE NIGHT HOURS TONIGHT.

KREIN

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

* LOW TO MEDIUM REGARDING CONVECTIVE TRENDS.

* MEDIUM TO HIGH REGARDING SOUTHWEST WINDS EXCEPT NEAR TSRA.

LENNING

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

SUNDAY NIGHT...VFR.

MONDAY...PERIODS OF TSRA LIKELY.

TUESDAY...SLIGHT CHANCE TSRA EARLY.

WEDNESDAY...SLIGHT CHANCE TSRA OVERNIGHT.

THURSDAY AND FRIDAY...CHANCE TSRA.

KREIN

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 301158
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
658 AM CDT Sat Aug 30 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 658 AM CDT SAT AUG 30 2014

Scattered showers continue this morning mainly east of KDEC and
could produce isolated MVFR cig/vsby. As daytime heating
begins...expecting intensification of thunderstorm activity.
Location/timing of thunderstorms still uncertain at this time so
have limited mention to VCTS after 16Z-18Z. After 00Z...drying
conditions expected to begin spreading eastward across Illinois.
Western TAF sites KPIA-KSPI likely to see fog formation overnight
while eastern TAF sites KDEC-KCMI could see continued showers
overnight until around 12Z and have left VCSH in forecast.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...ONTON
LONG TERM...07
AVIATION...ONTON






000
FXUS63 KILX 301158
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
658 AM CDT Sat Aug 30 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 658 AM CDT SAT AUG 30 2014

Scattered showers continue this morning mainly east of KDEC and
could produce isolated MVFR cig/vsby. As daytime heating
begins...expecting intensification of thunderstorm activity.
Location/timing of thunderstorms still uncertain at this time so
have limited mention to VCTS after 16Z-18Z. After 00Z...drying
conditions expected to begin spreading eastward across Illinois.
Western TAF sites KPIA-KSPI likely to see fog formation overnight
while eastern TAF sites KDEC-KCMI could see continued showers
overnight until around 12Z and have left VCSH in forecast.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...ONTON
LONG TERM...07
AVIATION...ONTON






000
FXUS63 KILX 301158
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
658 AM CDT Sat Aug 30 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 658 AM CDT SAT AUG 30 2014

Scattered showers continue this morning mainly east of KDEC and
could produce isolated MVFR cig/vsby. As daytime heating
begins...expecting intensification of thunderstorm activity.
Location/timing of thunderstorms still uncertain at this time so
have limited mention to VCTS after 16Z-18Z. After 00Z...drying
conditions expected to begin spreading eastward across Illinois.
Western TAF sites KPIA-KSPI likely to see fog formation overnight
while eastern TAF sites KDEC-KCMI could see continued showers
overnight until around 12Z and have left VCSH in forecast.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...ONTON
LONG TERM...07
AVIATION...ONTON






000
FXUS63 KILX 301158
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
658 AM CDT Sat Aug 30 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 658 AM CDT SAT AUG 30 2014

Scattered showers continue this morning mainly east of KDEC and
could produce isolated MVFR cig/vsby. As daytime heating
begins...expecting intensification of thunderstorm activity.
Location/timing of thunderstorms still uncertain at this time so
have limited mention to VCTS after 16Z-18Z. After 00Z...drying
conditions expected to begin spreading eastward across Illinois.
Western TAF sites KPIA-KSPI likely to see fog formation overnight
while eastern TAF sites KDEC-KCMI could see continued showers
overnight until around 12Z and have left VCSH in forecast.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...ONTON
LONG TERM...07
AVIATION...ONTON






000
FXUS63 KLOT 301140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA LATE MORNING THROUGH MIDDAY.

* SWLY WINDS GUSTING TO 18KT SATURDAY.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE THROUGH THE DAY TODAY AS THE AREA
REMAINS ENTRENCHED IN A WARM/MOIST AIRMASS. A WEAK COLD FRONT IS
EXPECTED TO MOVE ACROSS THE AREA TODAY IN ASSOCIATION WITH A
STRONGER UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD
PROVIDE SOME FOCUS FOR MORE THUNDERSTORM ACTIVITY. HOWEVER...THE
TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN THE TS
COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A TIME
BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL GUIDANCE
SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT MOVES
THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON HOURS.
HAVE OPTED TO GO WITH THE TEMPO GROUP FOR TS FOR THE MOST
FAVORABLE TIME FOR CONVECTIVE ACTIVITY OVER THE AREA...BUT THIS IS
STILL A LOW CONFIDENCE FORECAST.

WINDS SHOULD BECOME MORE SWLY WITH GUSTS TO 15-20KT FOR THE LATE
MORNING INTO EARLY EVENING AS SOME BREAKS IN THE OVERCAST ALLOWS
FOR SOME MIXING DOWN OF STRONGER WINDS ALOFT. WINDS SHOULD DROP
OFF AND BECOME LGT/VRBL OVERNIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA. WITH CLEARING SKIES...LIGHT WINDS AND AMPLE RESIDUAL LOW
LEVEL MOISTURE IN PLACE...THERE IS AN INCREASING CHANCE FOR FOG
AND STATUS TO DEVELOP DURG THE LATE NIGHT HOURS TONIGHT.

KREIN

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

* LOW CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

* MEDIUM CONFIDENCE IN MVFR/IFR CIGS/VIS LATE TONIGHT.

KREIN

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

SUNDAY NIGHT...VFR.

MONDAY...PERIODS OF TSRA LIKELY.

TUESDAY...SLIGHT CHANCE TSRA EARLY.

WEDNESDAY...SLIGHT CHANCE TSRA OVERNIGHT.

THURSDAY AND FRIDAY...CHANCE TSRA.

KREIN

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 301140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA LATE MORNING THROUGH MIDDAY.

* SWLY WINDS GUSTING TO 18KT SATURDAY.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE THROUGH THE DAY TODAY AS THE AREA
REMAINS ENTRENCHED IN A WARM/MOIST AIRMASS. A WEAK COLD FRONT IS
EXPECTED TO MOVE ACROSS THE AREA TODAY IN ASSOCIATION WITH A
STRONGER UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD
PROVIDE SOME FOCUS FOR MORE THUNDERSTORM ACTIVITY. HOWEVER...THE
TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN THE TS
COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A TIME
BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL GUIDANCE
SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT MOVES
THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON HOURS.
HAVE OPTED TO GO WITH THE TEMPO GROUP FOR TS FOR THE MOST
FAVORABLE TIME FOR CONVECTIVE ACTIVITY OVER THE AREA...BUT THIS IS
STILL A LOW CONFIDENCE FORECAST.

WINDS SHOULD BECOME MORE SWLY WITH GUSTS TO 15-20KT FOR THE LATE
MORNING INTO EARLY EVENING AS SOME BREAKS IN THE OVERCAST ALLOWS
FOR SOME MIXING DOWN OF STRONGER WINDS ALOFT. WINDS SHOULD DROP
OFF AND BECOME LGT/VRBL OVERNIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA. WITH CLEARING SKIES...LIGHT WINDS AND AMPLE RESIDUAL LOW
LEVEL MOISTURE IN PLACE...THERE IS AN INCREASING CHANCE FOR FOG
AND STATUS TO DEVELOP DURG THE LATE NIGHT HOURS TONIGHT.

KREIN

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

* LOW CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

* MEDIUM CONFIDENCE IN MVFR/IFR CIGS/VIS LATE TONIGHT.

KREIN

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

SUNDAY NIGHT...VFR.

MONDAY...PERIODS OF TSRA LIKELY.

TUESDAY...SLIGHT CHANCE TSRA EARLY.

WEDNESDAY...SLIGHT CHANCE TSRA OVERNIGHT.

THURSDAY AND FRIDAY...CHANCE TSRA.

KREIN

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 300903
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
403 AM CDT Sat Aug 30 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 1155 PM CDT FRI AUG 29 2014

Spotty showers and possibly a thunderstorm are expected across
central Illinois overnight, and some may impact a TAF site.
However, confidence in coverage/timing is too low to go above a
VCSH mention. By midday Saturday, a cold front will be pushing
into the area producing more numerous convection, with the bulk of
the precipitation apt to be thunderstorms. The highest coverage
should impact east central Illinois, including KDEC/KCMI. Still
plan to limit mention to VCTS at this time. By Saturday evening,
the front should be far enough east to end the threat at
KPIA/KBMI/KSPI, but KDEC/KCMI may still see a storm or two.
While predominantly VFR conditions are expected through the
period, MVFR or lower is briefly possible with thunderstorms.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...ONTON
LONG TERM...07
AVIATION...BAK







000
FXUS63 KILX 300903
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
403 AM CDT Sat Aug 30 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lift associated with an upper level shortwave trough over eastern
Iowa moving east-northeastward this morning is providing a focus for
a line of convection moving into western Illinois while a weaker
line of showers roughly along I-57 continues in eastern Illinois.
Cold front associated with the trough to our west is expected to
move to around to IA/IL border and stall out as the upper level
shortwave lifts northeastward bringing a continued focus for
precipitation for much of the next 24 hours. Rich moisture of close
to 2 inches will continue to stream into southeast Illinois to bring
the best chances for precipitation in that region. Tonight, as the
main trough shifts eastward, drier air continues to push eastward
allowing drier conditions to spread eastward into Illinois. As a
result, have pops trending downward overnight. Temperatures will be
down slightly today and tonight.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 401 AM CDT SAT AUG 30 2014

Lingered a chance of showers and thunderstorms over southeast IL
Sunday where more clouds will be over eastern/se IL. Best chances of
convection will be southeast of Ohio river across KY where short
wave energy will be. Highs in the low to mid 80s Sunday (warmest
over western areas) and humid with dewpoints mostly in the lower
70s. Dry conditions across area Sunday evening then have chance of
showers and thunderstorms returning to areas nw of I-55 overnight
Sunday night. This due to approaching strong upper level trof over
Pacific Northwest that brings a cold front se through IL Monday
night. Quite warm and humid again on Monday with highs in the 80s
and dewpoints in the lower to middle 70s. Chances of showers and
thunderstorms increase from nw to se during the day Monday with
highest chances Monday afternoon/evening, gradually shifting chances
se overnight Monday night. SPC has much of central IL in a slight
chance of severe storms Monday afternoon/evening for damaging winds
and large hail. Surface to 6km bulk shear around 40 kts and CAPES
2-3K J/Kg supports this risk of severe storms from I-70 nw.

Upper level flow to become zonal by middle of next week and frontal
boundary likely not to get too far south of IL. Thus will continue
chances of showers and thunderstorms Tue with best chances (40-50%)
in southeast IL closer to frontal boundary while slight chances nw
of IL river. Just slight chances by Wed-Thu night and quite warm and
humid with highs in the mid to upper 80s and even approaching
lower 90s over southern areas Thu and Friday. This is due to
upper level ridge of 593 dm 500 mb high building over KY/TN. Next
frontal boundary to press se toward IL later Friday into Saturday
of next week increasing chances of showers and thunderstorms followed
by cooler weather next weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 1155 PM CDT FRI AUG 29 2014

Spotty showers and possibly a thunderstorm are expected across
central Illinois overnight, and some may impact a TAF site.
However, confidence in coverage/timing is too low to go above a
VCSH mention. By midday Saturday, a cold front will be pushing
into the area producing more numerous convection, with the bulk of
the precipitation apt to be thunderstorms. The highest coverage
should impact east central Illinois, including KDEC/KCMI. Still
plan to limit mention to VCTS at this time. By Saturday evening,
the front should be far enough east to end the threat at
KPIA/KBMI/KSPI, but KDEC/KCMI may still see a storm or two.
While predominantly VFR conditions are expected through the
period, MVFR or lower is briefly possible with thunderstorms.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...ONTON
LONG TERM...07
AVIATION...BAK






000
FXUS63 KLOT 300849
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
349 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 300849
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
349 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 300849
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
349 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 300849
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
349 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 300846
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
346 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 300846
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
346 AM CDT SAT AUG 30 2014

.DISCUSSION...
344 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING THROUGH THE PERIOD...ALONG WITH THE THREAT FOR STRONG TO
SEVERE CONVECTION...ESPECIALLY MONDAY.

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES TWO MID/UPPER LEVEL
DISTURBANCES OF INTEREST FOR TODAY AND TONIGHTS WEATHER. THE FIRST IS
LOCATED OVER IOWA AND INTO EXTREME NORTHERN MISSOURI...AND THIS IS
DRIVING AN AREA OF SHOWERS AND SOME EMBEDDED STORMS INTO WESTERN
ILLINOIS AT THIS HOUR. THIS WAVE IS EXPECTED TO LIFT NORTHEASTWARD
ACROSS WISCONSIN LATER THIS MORNING...AND AS IT DOES SO...A FEW
SCATTERED SHOWERS AND A THUNDERSTORM OR TWO CAN BE EXPECTED ACROSS
NORTHERN ILLINOIS. A SECOND DISTURBANCE IS CURRENTLY LOCATED ACROSS
THE EASTERN DAKOTAS SOUTHWARD INTO EASTERN NEBRASKA. THIS WAVE IS
EXPECTED TO SHIFT EASTWARD ACROSS WISCONSIN AND NORTHERN ILLINOIS
DURING THE AFTERNOON TODAY. THESE TWO DISTURBANCES WILL HELP INDUCE
A UPPER LEVEL 60+ KT SPEED MAX ACROSS THE LOWER GREAT LAKES
REGION...ESSENTIALLY SETTING UP PORTIONS OF MY AREA TO LINE UP WITHIN
THE FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET MAX THIS
AFTERNOON AND INTO TONIGHT. THIS SHOULD HELP TO DRIVE AN AREA OF
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE AREA ALONG AND
AHEAD OF AN APPROACHING SURFACE COLD FRONT.

IT APPEARS THE BEST CHANCES FOR MORE ROBUST CONVECTIVE DEVELOPMENT
WILL BEGIN BY EARLY TO MID AFTERNOON OVER OR JUST TO THE SOUTH AND
EAST OF THE CHICAGO AREA. HIRES CONVECTIVE ALLOWING MODELS CONTINUE
TO INDICATE THE FAVORABLE LOCATIONS FOR AFTERNOON CONVECTIVE
ACTIVITY WILL PRIMARILY BE ALONG AND SOUTH OF A CHICAGO TO OTTAWA
LINE. ALTHOUGH MORNING SHOWERS AND CLOUD COVER COULD HAMPER
INSOLATION SOME ACROSS THE AREA...IT APPEARS THAT WITH DEW POINTS IN
THE LOWER 70S...MLCAPES SHOULD END UP AROUND 1500 J/KG...ESPECIALLY
ACROSS THE SOUTHEASTERN HALF OF MY AREA. THE INCREASING MID AND AN
UPPER LEVEL WIND FIELD ALSO LOOKS TO INCREASE THE DEEP LAYER SHEAR
UP TO 25 TO 30 KT...WHICH COULD SUPPORT A FEW STRONGER STORMS
CAPABLE OF STRONG WIND GUSTS. THESE STORMS WILL ALSO LIKELY PRODUCE
SOME TORRENTIAL DOWNPOURS GIVEN THE HIGH PWAT AIRMASS IN PLACE.
STORM MOTIONS OF 30 TO 40 KT SHOULD LIMIT THE RESIDENCE TIME OF
THESE STORMS OVER A GIVEN AREA...MAKING EXTREME RAINFALL AMOUNTS IN
A GIVEN AREA UNLIKELY.  THESE STORMS LOOK TO LINGER INTO THE
EVENING HOURS TONIGHT...ESPECIALLY ACROSS MY FAR SOUTHEASTERN
COUNTIES IN NORTHWESTERN INDIANA AND EAST CENTRAL ILLINOIS.

SUNDAY STILL APPEARS TO BE THE PICK DAY OF THE WEEKEND...WITH A
TEMPORARY BREAK FROM THE SHOWER AND THUNDERSTORM ACTIVITY...WHICH
WILL RETURN BY LABOR DAY. THE WEATHER PATTERN WILL BECOME ACTIVE
AGAIN EARLY NEXT WEEK AS A SIGNIFICANT UPPER LEVEL DISTURBANCE AND
ASSOCIATED SPEED MAX...EMANATING FROM THE NORTHEASTERN
PACIFIC...DIGS ACROSS THE NORTHERN CONUS. THIS LOOKS TO SUPPORT A
SURFACE LOW...WHICH SHOULD SHIFT NORTHEASTWARD ACROSS THE UPPER
MIDWEST AND INTO ONTARIO BY MONDAY. CONVECTIVE ACTIVITY...POSSIBLY
STRONG TO SEVERE WILL BE FAVORED LATE SUNDAY FROM KANSAS
NORTHEASTWARD ACROSS ACROSS IOWA AND MINNESOTA AHEAD OF AN
APPROACHING COLD FRONT. THIS COLD FRONT IS EXPECTED TO MOVE INTO
NORTHERN ILLINOIS DURING THE DAY MONDAY...AND IT APPEARS THE DIURNAL
TIMING OF THIS FRONT...AND UPPER LEVEL SYSTEM...COULD BE FAVORABLE
FOR STRONG TO SEVERE CONVECTION ACROSS THE AREA MONDAY AFTERNOON AND
EVENING...ESPECIALLY CONSIDERING THE DEEP LAYER SHEAR IS EXPECTED TO
BE MORE THAN ADEQUATE FOR ORGANIZED STRONG CONVECTION.

UNCERTAINTY INCREASES A BIT LATER MONDAY NIGHT INTO TUESDAY...AS THE
VARIOUS MODEL GUIDANCE ARE IN DISAGREEMENT IN HOW FAST THE SURFACE
COLD FRONT WILL PUSH ACROSS MY ENTIRE AREA. THE ECMWF IS SUGGESTING
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY INTO TUESDAY AS IT
SUGGESTS THAT ANOTHER MID LEVEL IMPULSE WILL SHIFT OVER THE AREA
LEADING TO THE DEVELOPMENT OF A SECONDARY SURFACE LOW OVER THE AREA.
IF THIS SOLUTION WERE TO PAN OUT...IT COULD SET THE STAGE FOR SOME
VERY HEAVY RAINFALL AMOUNTS ACROSS PORTIONS OF THE AREA INTO TUESDAY
MORNING.

DURING THE MID TO LATER PORTION OF THE WEEK IT APPEARS THINGS WILL
BE ON A WARMING TREND...ESPECIALLY BY THURSDAY AS MID LEVEL HEIGHTS
BUILD SUBSTANTIALLY ACROSS THE AREA. THIS COULD LEAD TO A RUN AT
UPPER 80 TO LOWER 90 TEMPERATURES FOR THURSDAY. I CONTINUED WITH
SLIGHT CHANCE POPS DURING THE LATER PERIOD...MAINLY DUE TO
UNCERTAINTIES ON WHETHER OR NOT ANY SMALL SCALE DISTURBANCES WILL TRY
TO SPARK OFF CONVECTION OVER THE AREA. HOWEVER...WITH THE BUILDING
HEIGHTS AND WARMING TEMPERATURES ALOFT...THE AREA COULD END UP
CAPPED TO CONVECTIVE DEVELOPMENT ON WEDNESDAY AND THURSDAY.

KJB

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 300758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 AM CDT SAT AUG 30 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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





000
FXUS63 KLOT 300758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 AM CDT SAT AUG 30 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
300 AM CDT

A PERIOD OF ACTIVE WEATHER IS SETTING UP FOR LAKE MICHIGAN FOR
THE NEXT SEVERAL DAYS. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL
TRACK ACROSS THE UPPER GREAT LAKES REGION INTO CANADA DRAGGING
WEAK COLD FRONTS ACROSS THE LAKE. MODERATE SOUTH TO SOUTHWESTERLY
WINDS WILL PERSIST ACROSS THE LAKE THROUGH MUCH OF SATURDAY UNTIL
THE FIRST OF THE COLD FRONTS SWEEPS ACROSS THE LAKE LATE THIS
AFTERNOON AND THIS EVENING...TURNING WINDS TO NORTHWESTERLY
TONIGHT. A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY BUILD IN
BEHIND THE FRONT...ALLOWING WINDS TO DROP OFF AND BECOME MORE
VARIABLE IN DIRECTION EARLY SUNDAY. BY SUNDAY AFTERNOON...ANOTHER
DEVELOPING LOW OVER THE NORTHERN PLAINS WILL LEAD TO STRENGTHENING
SOUTHERLY WINDS FOR MONDAY AND MONDAY EVENING...UP TO 25 KT...BUT
THE NEXT FRONT WILL CROSS THE LAKE MONDAY NIGHT. THIS FRONTAL
PASSAGE WILL NOT BE AS ABRUPT AS THE FIRST WITH WINDS ONLY VEERING
SOUTHWESTERLY. WINDS SHOULD INCREASE AGAIN TO UP TO 25KT
IMMEDIATELY FOLLOWING THE FRONTAL PASSAGE MONDAY NIGHT...BUT SHOULD
THEN WEAKEN SLIGHTLY INTO MIDWEEK WHILE REMAINING GENERALLY
SOUTHWESTERLY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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






000
FXUS63 KLOT 300557
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1257 AM CDT SAT AUG 30 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA MIDDAY SATURDAY

* SWLY WINDS GUSTING TO 20KT SATURDAY AFTERNOON.

KREIN

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

SCT SHRA AND ISOLD TSRA CONTINUE AS THE AREA REMAINS ENTRENCHED IN
A WARM/MOIST AIRMASS. IN THE ABSENCE OF ANY SFC OR MID LEVEL
FOCUS...PCPN SHOULD REMAIN FAIRLY ISOLATED. HAVE BEEN TRACKING A
A FEW PATCHES OF PERSISTENT RAIN MOVING INTO NCNTRL/NERN IL WHICH
SHOULD HOLD TOGETHER LONG ENOUGH TO BRING SOME WETTING RAIN TO
THE CHICAGO AREA TERMINALS. HOWEVER...ANY PCPN SHOULD BE FLEETING.
FOR THE REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING...WILL
CARRY A DRY FORECAST THOUGH THERE SHOULD BE SOME SCT SHRA OR ISOLD
TSRA WITH LITTLE CHANGE IN THE AIRMASS.

BY TOMORROW MORNING...THE SHORT TERM MODEL GUIDANCE IS PUSHING A
WEAK COLD FRONT ACROSS THE AREA IN ASSOCIATION WITH A STRONGER
UPPER LEVEL TROUGH. THE UPPER TROUGH AND SFC FRONT SHOULD PROVIDE
BETTER FOCUS FOR MORE ORGANIZED THUNDERSTORMS ACTIVITY.
HOWEVER...THE TIMING OF THE FRONT WILL PLAY A SIGNIFICANT ROLE IN
THE TS COVERAGE AS IT SHOULD MOVE NRN IL BY LATE MORNING...AT A
TIME BEFORE MAX DIURNAL WARMING. THE HIGH RESOLUTION MODEL
GUIDANCE SUGGESTS THAT TS COVERAGE SHOULD INCREASE AS THE FRONT
MOVES THROUGH ECNTRL IL AND NWRN IN DURG THE EARLY AFTERNOON
HOURS. SO...WILL MAINTAIN THE PROB30 GROUP FOR THE TIME THAT THE
FRONT SHOULD BE INVOF THE TERMINALS...THOUGH THERE IS A BETTER
CHANCE FOR MORE ORGANIZED...WIDESPREAD TS INVOF THE COLD FRONT AS
IT PUSHES SOUTH AND EAST OF THE TERMINALS SATURDAY AFTERNOON.

WINDS SHOULD GENERALLY BE SOUTHERLY AT LESS THAN 10KT THROUGH THE
REMAINDER OF THE NIGHT AND INTO SATURDAY MORNING. AS THE TROUGH
ASSOCIATED WITH THE COLD FRONT APPROACHES THE REGION...WINDS
SHOULD BECOME MORE SWLY WITH GUSTS TO ARND 20KT FOR THE LATE
MORNING INTO EARLY EVENING. WINDS SHOULD DROP OFF AND BECOME
LGT/VRBL OVERNIGHT SATURDAY NIGHT AS HIGH PRESSURE SPREADS ACROSS
THE AREA.

KREIN

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS.

* MEDIUM-HIGH CONFIDENCE IN WINDS.

KREIN

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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






000
FXUS63 KILX 300456
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1156 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 900 PM CDT FRI AUG 29 2014

Weakening line of convection continues to push across west central
Illinois this evening. Not too much precipitation has filled in
between this line/weak trof and main cold front, which extends
from upper Midwest into central Plains. Expect this should
continue to be the case as the best low level jet/upper dynamics
will remain closer to the front. So, plan to adjust PoPs downward
a bit for the rest of the night (away from and behind current
line). Remainder of forecast looks pretty good.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 1155 PM CDT FRI AUG 29 2014

Spotty showers and possibly a thunderstorm are expected across
central Illinois overnight, and some may impact a TAF site.
However, confidence in coverage/timing is too low to go above a
VCSH mention. By midday Saturday, a cold front will be pushing
into the area producing more numerous convection, with the bulk of
the precipitation apt to be thunderstorms. The highest coverage
should impact east central Illinois, including KDEC/KCMI. Still
plan to limit mention to VCTS at this time. By Saturday evening,
the front should be far enough east to end the threat at
KPIA/KBMI/KSPI, but KDEC/KCMI may still see a storm or two.
While predominantly VFR conditions are expected through the
period, MVFR or lower is briefly possible with thunderstorms.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BAK
SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KILX 300456
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1156 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 900 PM CDT FRI AUG 29 2014

Weakening line of convection continues to push across west central
Illinois this evening. Not too much precipitation has filled in
between this line/weak trof and main cold front, which extends
from upper Midwest into central Plains. Expect this should
continue to be the case as the best low level jet/upper dynamics
will remain closer to the front. So, plan to adjust PoPs downward
a bit for the rest of the night (away from and behind current
line). Remainder of forecast looks pretty good.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 1155 PM CDT FRI AUG 29 2014

Spotty showers and possibly a thunderstorm are expected across
central Illinois overnight, and some may impact a TAF site.
However, confidence in coverage/timing is too low to go above a
VCSH mention. By midday Saturday, a cold front will be pushing
into the area producing more numerous convection, with the bulk of
the precipitation apt to be thunderstorms. The highest coverage
should impact east central Illinois, including KDEC/KCMI. Still
plan to limit mention to VCTS at this time. By Saturday evening,
the front should be far enough east to end the threat at
KPIA/KBMI/KSPI, but KDEC/KCMI may still see a storm or two.
While predominantly VFR conditions are expected through the
period, MVFR or lower is briefly possible with thunderstorms.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BAK
SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK






000
FXUS63 KLOT 300334
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1034 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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






000
FXUS63 KLOT 300334
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1034 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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






000
FXUS63 KLOT 300334
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1034 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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






000
FXUS63 KLOT 300334
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1034 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* CHANCE OF SHRA/TSRA THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI

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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 3 AM SATURDAY.

&&

$$

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

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






000
FXUS63 KILX 300210
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
910 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 900 PM CDT FRI AUG 29 2014

Weakening line of convection continues to push across west central
Illinois this evening. Not too much precipitation has filled in
between this line/weak trof and main cold front, which extends
from upper Midwest into central Plains. Expect this should
continue to be the case as the best low level jet/upper dynamics
will remain closer to the front. So, plan to adjust PoPs downward
a bit for the rest of the night (away from and behind current
line). Remainder of forecast looks pretty good.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 654 PM CDT FRI AUG 29 2014

A weakening band of showers and thunderstorms occurring along a
weak surface trof is pushing into the central Illinois terminal
area from the west. This weakening trend is expected to persist
with the loss of diurnal heating. That being said, a brief period
of precipitation is likely this evening at the terminals. Have
included a two hour TEMPO group to cover the arrival of this
convective line or its remnants. Then, the best chance of
showers/storms this TAF period is expected from the midday hours
Saturday, continuing through the afternoon. This precipitation
will occur along a slow moving cold front that is currently
resides in the Plains. However, given the uncertainty in explicit
timing and/or coverage along/ahead of the front, have only
included a VCTS mention for now. While predominantly VFR conditions
are expected through the period, MVFR or lower is briefly possible
with thunderstorms.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BAK
SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KILX 300210
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
910 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 900 PM CDT FRI AUG 29 2014

Weakening line of convection continues to push across west central
Illinois this evening. Not too much precipitation has filled in
between this line/weak trof and main cold front, which extends
from upper Midwest into central Plains. Expect this should
continue to be the case as the best low level jet/upper dynamics
will remain closer to the front. So, plan to adjust PoPs downward
a bit for the rest of the night (away from and behind current
line). Remainder of forecast looks pretty good.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 654 PM CDT FRI AUG 29 2014

A weakening band of showers and thunderstorms occurring along a
weak surface trof is pushing into the central Illinois terminal
area from the west. This weakening trend is expected to persist
with the loss of diurnal heating. That being said, a brief period
of precipitation is likely this evening at the terminals. Have
included a two hour TEMPO group to cover the arrival of this
convective line or its remnants. Then, the best chance of
showers/storms this TAF period is expected from the midday hours
Saturday, continuing through the afternoon. This precipitation
will occur along a slow moving cold front that is currently
resides in the Plains. However, given the uncertainty in explicit
timing and/or coverage along/ahead of the front, have only
included a VCTS mention for now. While predominantly VFR conditions
are expected through the period, MVFR or lower is briefly possible
with thunderstorms.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BAK
SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK






000
FXUS63 KILX 292354
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
654 PM CDT Fri Aug 29 2014

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 654 PM CDT FRI AUG 29 2014

A weakening band of showers and thunderstorms occurring along a
weak surface trof is pushing into the central Illinois terminal
area from the west. This weakening trend is expected to persist
with the loss of diurnal heating. That being said, a brief period
of precipitation is likely this evening at the terminals. Have
included a two hour TEMPO group to cover the arrival of this
convective line or its remnants. Then, the best chance of
showers/storms this TAF period is expected from the midday hours
Saturday, continuing through the afternoon. This precipitation
will occur along a slow moving cold front that is currently
resides in the Plains. However, given the uncertainty in explicit
timing and/or coverage along/ahead of the front, have only
included a VCTS mention for now. While predominantly VFR conditions
are expected through the period, MVFR or lower is briefly possible
with thunderstorms.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KILX 292354
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
654 PM CDT Fri Aug 29 2014

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 654 PM CDT FRI AUG 29 2014

A weakening band of showers and thunderstorms occurring along a
weak surface trof is pushing into the central Illinois terminal
area from the west. This weakening trend is expected to persist
with the loss of diurnal heating. That being said, a brief period
of precipitation is likely this evening at the terminals. Have
included a two hour TEMPO group to cover the arrival of this
convective line or its remnants. Then, the best chance of
showers/storms this TAF period is expected from the midday hours
Saturday, continuing through the afternoon. This precipitation
will occur along a slow moving cold front that is currently
resides in the Plains. However, given the uncertainty in explicit
timing and/or coverage along/ahead of the front, have only
included a VCTS mention for now. While predominantly VFR conditions
are expected through the period, MVFR or lower is briefly possible
with thunderstorms.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK






000
FXUS63 KLOT 292348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLINOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* SLIGHT CHANCE OF BRIEF WIND SHIFT TO MORE EASTERLY WITH TS
  OUTFLOW/LAKE BREEZE EARLY THIS EVENING
* ISOLD TSRA MOSTLY JUST AVOIDING TERMINALS THRU MID EVENING
* CHANCE OF SHRA/TSRA LATE EVENING THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI


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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 292348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLINOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* SLIGHT CHANCE OF BRIEF WIND SHIFT TO MORE EASTERLY WITH TS
  OUTFLOW/LAKE BREEZE EARLY THIS EVENING
* ISOLD TSRA MOSTLY JUST AVOIDING TERMINALS THRU MID EVENING
* CHANCE OF SHRA/TSRA LATE EVENING THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI


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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

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

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 292220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* ISOLATED SHRA/TSRA THRU EARLY EVENING

* S-SSE WINDS 10-14KT THRU EARLY EVENING

* ANOTHER PERIOD OF SHRA/TSRA TOWARD MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER/IZZI

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA WILL CONTINUE TO DEVELOP IN VC OF THE TERMINALS
THROUGH EARLY EVENING. COVERAGE WILL BE LOW BUT COULD SEE BRIEF
SHRA OR TSRA AT CHICAGO AREA TERMINALS THROUGH ABOUT 00-01Z.

IZZI

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER/IZZI

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 292220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* ISOLATED SHRA/TSRA THRU EARLY EVENING

* S-SSE WINDS 10-14KT THRU EARLY EVENING

* ANOTHER PERIOD OF SHRA/TSRA TOWARD MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER/IZZI

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA WILL CONTINUE TO DEVELOP IN VC OF THE TERMINALS
THROUGH EARLY EVENING. COVERAGE WILL BE LOW BUT COULD SEE BRIEF
SHRA OR TSRA AT CHICAGO AREA TERMINALS THROUGH ABOUT 00-01Z.

IZZI

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER/IZZI

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 292120 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 292120 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 292120
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 292120
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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:
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000
FXUS63 KILX 292003
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
303 PM CDT Fri Aug 29 2014

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.


&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.


&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES







000
FXUS63 KILX 292003
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
303 PM CDT Fri Aug 29 2014

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.


&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.


&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES







000
FXUS63 KILX 292003
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
303 PM CDT Fri Aug 29 2014

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.


&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.


&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES







000
FXUS63 KILX 292003
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
303 PM CDT Fri Aug 29 2014

.SHORT TERM...(This evening through Saturday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

19z/2pm surface analysis shows warm front extending from southern
Minnesota to southern Indiana, generally along the I-74 corridor
across central Illinois.  Widely scattered showers and thunderstorms
have developed along the front and will continue to do so for the
balance of the afternoon.  Meanwhile further upstream, a trough of
low pressure is evident across central Missouri where thunderstorms
are becoming more numerous.  As this trough shifts northeastward,
storm chances will begin to increase across southwest Illinois early
this evening, then across the entire KILX CWA by mid to late
evening.  May see a gradual decrease in areal coverage as daytime
instability is lost, so will keep PoPs in the 50-60 range tonight.
As has been the case for the past several days, any storms that
occur will be capable of frequent lightning and very high rainfall
rates of 1.5 to 2 inches per hour.

The trough axis will lift northeast of the area late tonight into
Saturday morning, with only scattered showers/storms lingering early
in the day.  As a cold front currently across the Plains pushes
eastward and interacts with the very moist airmass in place across
the region, a renewed round of convection will be likely Saturday
afternoon/evening.  Will carry high chance PoPs in the Illinois
River Valley and likely further east across the remainder of the CWA
accordingly.


&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 302 PM CDT FRI AUG 29 2014

In the wake of Saturdays precip, the boundary at the sfc slows and
becomes a bit more diffuse overall and models are starting to speed
up the clearing as the boundary slips to the southeast into the Ohio
River Valley.  Though precip chances linger in southern and east
central Illinois on Saturday night, Sunday may be a break in the
widespread chances for rain.  Next wave slowing in the 12z runs of
the ECMWF and the NAM...though the wave aloft is slowing, the GFS
qpf is slower to respond.  Postponing the pops resulting in a dry
Sunday evening for the eastern half of the state with pops
increasing in the overnight hours along and west of Interstate 55,
with precip spreading and dominating much of the day on Monday.
Given the high PW values in the atmosphere, heavy rains will remain
a threat for the forecast pd.  Delaying the onset of precip from
Sunday night into Monday also resulting in a prolonging into Monday
night. Question for the models beyond Monday night really revolving
around the boundary stalling in quasi zonal flow aloft not really
supporting any major progression of the sfc boundary and yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Whereas the GFS is pushing a series of MCSs on the edge of the weak
flow, the ECMWF is far more conservative...though both models are
tempering the amplification significantly over the latter half of
the work week.  Thermal ridging in the south keeps above normal
temps over the region.


&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES







000
FXUS63 KLOT 291958
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 291958
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO










000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 20Z...

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 291807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
107 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 291807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
107 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 291750
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1250 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...BARNES






000
FXUS63 KILX 291750
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1250 PM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1250 PM CDT FRI AUG 29 2014

Widely scattered thunderstorms will continue to develop across
central Illinois over the next couple of hours as a warm front
lifts north of the area. Will carry VCTS at all terminals
accordingly. Meanwhile further upstream, regional radar mosaic is
showing a band of showers/thunder developing across western
Missouri into northern Arkansas. HRRR is showing this band lifting
N/NE this afternoon, eventually arriving in west-central Illinois
early this evening. Have therefore opted to carry predominant
light rain with VCTS for a 6-hour period at all sites this evening
into the overnight hours. Based on HRRR and observed trends, have
brought precip into KSPI after 02z, then further east to KCMI
after 05z. After this initial band lifts through the area, only
widely scattered showers will be noted Saturday morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...BARNES







000
FXUS63 KLOT 291608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1108 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED TSRA THIS AFTERNOON/EARLY EVENING.

* SOUTH-SOUTHEAST WIND AROUND 10 KT BECOMING SOUTH WITH GUSTS NEAR
  20 KT DEVELOPING BY MIDDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

RATZER

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* MEDIUM-LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN/RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 291608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1108 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED TSRA THIS AFTERNOON/EARLY EVENING.

* SOUTH-SOUTHEAST WIND AROUND 10 KT BECOMING SOUTH WITH GUSTS NEAR
  20 KT DEVELOPING BY MIDDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

RATZER

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* MEDIUM-LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN/RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 291449
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
949 AM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 658 AM CDT FRI AUG 29 2014

Mainly VFR conditions this morning although areas of light fog
with MVFR visibilities exist mainly from KTAZ-KCMI eastward. By
14Z all MVFR visibility due to fog expected to dissipate. From
around 15Z-17Z isolated TSRA expected to develop and continue
through the afternoon although probability of occurrence at TAF
sites too low for explicit mention in TEMPO groups for now. Chances
will increase in the evening from KSPI-KPIA westward as a cold
front approaches. This will spread eastward overnight. Timing
remains difficult to pinpoint until the arrival time nears. So,
have limited mention to VCTS. Storms, if they impact a terminal,
may briefly reduce cigs/vsbys to MVFR or lower.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...ONTON







000
FXUS63 KILX 291449
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
949 AM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 658 AM CDT FRI AUG 29 2014

Mainly VFR conditions this morning although areas of light fog
with MVFR visibilities exist mainly from KTAZ-KCMI eastward. By
14Z all MVFR visibility due to fog expected to dissipate. From
around 15Z-17Z isolated TSRA expected to develop and continue
through the afternoon although probability of occurrence at TAF
sites too low for explicit mention in TEMPO groups for now. Chances
will increase in the evening from KSPI-KPIA westward as a cold
front approaches. This will spread eastward overnight. Timing
remains difficult to pinpoint until the arrival time nears. So,
have limited mention to VCTS. Storms, if they impact a terminal,
may briefly reduce cigs/vsbys to MVFR or lower.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...ONTON







000
FXUS63 KILX 291449
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
949 AM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 658 AM CDT FRI AUG 29 2014

Mainly VFR conditions this morning although areas of light fog
with MVFR visibilities exist mainly from KTAZ-KCMI eastward. By
14Z all MVFR visibility due to fog expected to dissipate. From
around 15Z-17Z isolated TSRA expected to develop and continue
through the afternoon although probability of occurrence at TAF
sites too low for explicit mention in TEMPO groups for now. Chances
will increase in the evening from KSPI-KPIA westward as a cold
front approaches. This will spread eastward overnight. Timing
remains difficult to pinpoint until the arrival time nears. So,
have limited mention to VCTS. Storms, if they impact a terminal,
may briefly reduce cigs/vsbys to MVFR or lower.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...ONTON







000
FXUS63 KILX 291449
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
949 AM CDT Fri Aug 29 2014

.UPDATE...
ISSUED AT 948 AM CDT FRI AUG 29 2014

Made a quick update to the forecast to raise PoPs from Lincoln
northward to Henry due to current radar trends. A cluster of
thunderstorms with high rainfall rates of 1.5 to 2 inches per hour
is lifting northward into Tazewell and western McLean counties at
this time and will continue northward across Woodford and Marshall
counties over the next couple of hours. Once this cluster
weakens/exits the KILX CWA toward midday, additional showers/storms
will develop along outflow boundaries as well as the synoptic warm
front as it pushes northward later today. Have gone with low
chance PoPs across the board this afternoon, with highs climbing
well into the 80s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 658 AM CDT FRI AUG 29 2014

Mainly VFR conditions this morning although areas of light fog
with MVFR visibilities exist mainly from KTAZ-KCMI eastward. By
14Z all MVFR visibility due to fog expected to dissipate. From
around 15Z-17Z isolated TSRA expected to develop and continue
through the afternoon although probability of occurrence at TAF
sites too low for explicit mention in TEMPO groups for now. Chances
will increase in the evening from KSPI-KPIA westward as a cold
front approaches. This will spread eastward overnight. Timing
remains difficult to pinpoint until the arrival time nears. So,
have limited mention to VCTS. Storms, if they impact a terminal,
may briefly reduce cigs/vsbys to MVFR or lower.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...ONTON







000
FXUS63 KLOT 291403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED TSRA THIS AFTERNOON/EARLY EVENING.

* SOUTH-SOUTHEAST WIND AROUND 10 KT BECOMING SOUTH WITH GUSTS NEAR
  20 KT DEVELOPING BY MIDDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

RATZER

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* MEDIUM-LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN/RATZER

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KILX 291158
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
658 AM CDT Fri Aug 29 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 658 AM CDT FRI AUG 29 2014


Mainly VFR conditions this morning although areas of light fog
with MVFR visibilities exist mainly from KTAZ-KCMI eastward. By
14Z all MVFR visibility due to fog expected to dissipate. From
around 15Z-17Z isolated TSRA expected to develop and continue
through the afternoon although probability of occurrence at TAF
sites too low for explicit mention in TEMPO groups for now. Chances
will increase in the evening from KSPI-KPIA westward as a cold
front approaches. This will spread eastward overnight. Timing
remains difficult to pinpoint until the arrival time nears. So,
have limited mention to VCTS. Storms, if they impact a terminal,
may briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...ONTON







000
FXUS63 KILX 291158
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
658 AM CDT Fri Aug 29 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 658 AM CDT FRI AUG 29 2014


Mainly VFR conditions this morning although areas of light fog
with MVFR visibilities exist mainly from KTAZ-KCMI eastward. By
14Z all MVFR visibility due to fog expected to dissipate. From
around 15Z-17Z isolated TSRA expected to develop and continue
through the afternoon although probability of occurrence at TAF
sites too low for explicit mention in TEMPO groups for now. Chances
will increase in the evening from KSPI-KPIA westward as a cold
front approaches. This will spread eastward overnight. Timing
remains difficult to pinpoint until the arrival time nears. So,
have limited mention to VCTS. Storms, if they impact a terminal,
may briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...ONTON






000
FXUS63 KLOT 291152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* SCATTERED TSRA/SHRA FRIDAY LATE AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

KREIN

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 291152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* SCATTERED TSRA/SHRA FRIDAY LATE AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

KREIN

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 291152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* SCATTERED TSRA/SHRA FRIDAY LATE AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

KREIN

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 291152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* SCATTERED TSRA/SHRA FRIDAY LATE AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

KREIN

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN

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

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 290838
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
338 AM CDT Fri Aug 29 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.


&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.


&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1156 PM CDT THU AUG 28 2014

The new 06Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered showers/storms are possible. Initially the main
precipitation threat will be diurnally driven on Friday, but
chances will also be increasing Friday evening with the approach
of a cold front. As such, it is difficult to pinpoint
precipitation until it is closer to arrival time. So, have limited
most mention to VCTS. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...BAK






000
FXUS63 KILX 290838
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
338 AM CDT Fri Aug 29 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Frontal boundary from NW Missouri through southern Illinois into
Kentucky will push northward today as southwesterly flow increases
ahead of a trough currently over the central plains. For this
afternoon convection will be primarily driven by surface heating and
not well organized, therefore have ramped up pops through early
afternoon and trended them downward in early evening in eastern IL.
In the early evening, the upper level trough and weak surface cold
front associated with the plains system begin to move into western
IL. This will bring a good chance of showers and thunderstorms
pushing across central and southeast IL overnight. Temperatures for
today will be similar to Thursdays...generally mid to upper 80s with
dew points in the low 70s resulting in heat index values in the low
to mid 90s.


&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 337 AM CDT FRI AUG 29 2014

Cold front accompanying current deep Plains upper trough will be
losing some of its punch as it comes into the mid-Mississippi
Valley, but will still be potent enough for showers and
thunderstorms to be likely on Saturday over our area. Some heavier
rains will be possible with the stronger storms, primarily over the
southeast CWA where precipitable water values will be around 1.8
inches Saturday afternoon, about 2 standard deviations above normal
for the end of August. The precipitation threat will continue
Saturday night and Sunday over the southeast CWA as moisture
continues to surge into the Ohio Valley. However, the northwest half
of the forecast area should be dry during this period.

West-east upper high to dominate the lower CONUS into mid week, as a
broad trough tracks across the northern states. Showers and storms
ahead of the surface front should begin spreading in northwest of
the I-55 corridor after midnight Sunday night. Most of the models
try to form some sort of dual MCS`s, one tracking east across
Wisconsin and the other southwest through Missouri, with some
potential for lesser amounts of rain Monday morning. However,
redevelopment is expected by afternoon as the front starts to hang
up in the upper flow, so have likely PoP`s over most of the CWA for
Monday. With the frontal boundary in the vicinity, the 00Z models
are trending more toward additional MCS activity tracking over our
forecast area Monday night. Have increased the PoP`s some,
especially across the north which had been dry Monday night. The
front should start to be dragged a bit further south on Tuesday as a
surface wave moves along it, but have kept PoP`s in the 30-40% range
into Tuesday night before the focus shifts more into the Ohio Valley.

Mid to late week, the upper high begins to ridge again across the
Mississippi Valley. 850 mb temperatures of 20-22C should allow for
highs to return to the 90s late next week.


&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1156 PM CDT THU AUG 28 2014

The new 06Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered showers/storms are possible. Initially the main
precipitation threat will be diurnally driven on Friday, but
chances will also be increasing Friday evening with the approach
of a cold front. As such, it is difficult to pinpoint
precipitation until it is closer to arrival time. So, have limited
most mention to VCTS. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...ONTON
LONG TERM...GEELHART
AVIATION...BAK







000
FXUS63 KLOT 290831
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290815
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290815
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290815
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290815
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

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

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

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

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KILX 290459
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1159 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1156 PM CDT THU AUG 28 2014

The new 06Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered showers/storms are possible. Initially the main
precipitation threat will be diurnally driven on Friday, but
chances will also be increasing Friday evening with the approach
of a cold front. As such, it is difficult to pinpoint
precipitation until it is closer to arrival time. So, have limited
most mention to VCTS. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KILX 290459
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1159 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1156 PM CDT THU AUG 28 2014

The new 06Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered showers/storms are possible. Initially the main
precipitation threat will be diurnally driven on Friday, but
chances will also be increasing Friday evening with the approach
of a cold front. As such, it is difficult to pinpoint
precipitation until it is closer to arrival time. So, have limited
most mention to VCTS. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KILX 290459
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1159 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1156 PM CDT THU AUG 28 2014

The new 06Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered showers/storms are possible. Initially the main
precipitation threat will be diurnally driven on Friday, but
chances will also be increasing Friday evening with the approach
of a cold front. As such, it is difficult to pinpoint
precipitation until it is closer to arrival time. So, have limited
most mention to VCTS. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KILX 290459
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1159 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1156 PM CDT THU AUG 28 2014

The new 06Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered showers/storms are possible. Initially the main
precipitation threat will be diurnally driven on Friday, but
chances will also be increasing Friday evening with the approach
of a cold front. As such, it is difficult to pinpoint
precipitation until it is closer to arrival time. So, have limited
most mention to VCTS. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KLOT 290308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

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

* LOW-MEDIUM IN PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

* HIGH IN WIND DIR/SPEED AND TRENDS

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 290308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

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

* LOW-MEDIUM IN PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

* HIGH IN WIND DIR/SPEED AND TRENDS

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 290020
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
720 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 705 PM CDT THU AUG 28 2014

The new 00Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered, mainly diurnally driven showers/storms are
possible. As such, it is difficult to pinpoint precipitation until
it is closer to arrival time. So, have limited most mention to
VCTS during the day (aside from a few TEMPOs in the first 6 hours
based on radar trends. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK






000
FXUS63 KILX 290020
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
720 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 705 PM CDT THU AUG 28 2014

The new 00Z TAF valid time is expected to be much like the past
couple. Predominantly VFR/quiet weather conditions are expected.
However, scattered, mainly diurnally driven showers/storms are
possible. As such, it is difficult to pinpoint precipitation until
it is closer to arrival time. So, have limited most mention to
VCTS during the day (aside from a few TEMPOs in the first 6 hours
based on radar trends. Storms, if they impact a terminal, may
briefly reduce cigs/vsbys to MVFR or lower.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BAK







000
FXUS63 KLOT 290014
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
714 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

&&

.PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 290014
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
714 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

&&

.PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290013
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
713 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD


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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD


&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 290013
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
713 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD


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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD


&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 282234
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
534 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* EAST WIND ARND 8-10KT THRU LATE AFTN...WINDS TURNING SE LATER
  THIS EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL TSRA AFT 09Z
  THRU DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER/KMD

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* MEDIUM HIGH CONFIDENCE IN -SHRA 0Z-3Z.

* MEDIUM-HIGH CONFIDENCE THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE AFTER FIRST
  ROUND OF SHOWERS THIS EVENING.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 282234
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
534 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* EAST WIND ARND 8-10KT THRU LATE AFTN...WINDS TURNING SE LATER
  THIS EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL TSRA AFT 09Z
  THRU DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER/KMD

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* MEDIUM HIGH CONFIDENCE IN -SHRA 0Z-3Z.

* MEDIUM-HIGH CONFIDENCE THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE AFTER FIRST
  ROUND OF SHOWERS THIS EVENING.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 282234
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
534 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* EAST WIND ARND 8-10KT THRU LATE AFTN...WINDS TURNING SE LATER
  THIS EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL TSRA AFT 09Z
  THRU DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER/KMD

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* MEDIUM HIGH CONFIDENCE IN -SHRA 0Z-3Z.

* MEDIUM-HIGH CONFIDENCE THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE AFTER FIRST
  ROUND OF SHOWERS THIS EVENING.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 282234
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
534 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* EAST WIND ARND 8-10KT THRU LATE AFTN...WINDS TURNING SE LATER
  THIS EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL TSRA AFT 09Z
  THRU DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER/KMD

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* MEDIUM HIGH CONFIDENCE IN -SHRA 0Z-3Z.

* MEDIUM-HIGH CONFIDENCE THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE AFTER FIRST
  ROUND OF SHOWERS THIS EVENING.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER/KMD

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 281955
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
255 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.


&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES







000
FXUS63 KILX 281955
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
255 PM CDT Thu Aug 28 2014

.SHORT TERM...(This evening through Friday)
ISSUED AT 255 PM CDT THU AUG 28 2014

18z/1pm surface map shows warm front extending from northern
Missouri into western Kentucky.  Aloft...vigorous upper-level low is
evident on water vapor imagery over eastern Colorado/western Kansas.
Large cluster of showers/storms associated with the low developed
along the front across Iowa last night and has since weakened as it
lifted northeastward into drier air over the Upper Midwest/Great
Lakes.  Convection is still ongoing along outflow boundary from
eastern Iowa into northern Missouri: however, most of this will
remain W/NW of the KILX CWA late this afternoon into the early
evening.  Meanwhile, scattered convection is firing further south
along the front across western Kentucky and this is expected to
develop further north into central Illinois over the next couple of
hours.  HRRR has had a good handle on the convection and have
followed its solution closely for the immediate short-term.  Have
therefore gone with scattered showers/thunder across all but the far
NE CWA around Champaign and Danville this afternoon into the
evening.  Think convection will be diurnally driven and will
dissipate shortly after sunset.

As upper low slowly approaches from the west, corresponding
downstream ridging will help push the warm front northward tonight
into Friday.  With strongest upper support remaining west of
Illinois through the day, think convection will once again only be
scattered in nature and primarily occur during peak heating.  Have
therefore gone with a mostly dry forecast during the morning,
followed by chance PoPs during the afternoon.  Best rain chances
will be focused closer to the frontal boundary across the northern
two-thirds of the CWA.  High temperatures on Friday will be held
down a bit by clouds/precip, but will still rise well into the 80s,
with locations along/south of I-70 perhaps hitting the 90-degree
mark.


&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 255 PM CDT THU AUG 28 2014

Upper wave currently over the Rockies expected to slowly move out
and bring rain chances to the area, particularly Friday night and
Saturday as the upper trof moves through the Midwest.  Keeping the
precip around on Saturday may result in slightly cooler temperatures
by the afternoon.  Once again, the cold front associated with the
upper trof moves across the region, losing its distinct baroclinic
zone and becoming more diffuse as it slows considerably just to the
southeast near the Ohio River Valley.  The remaining boundary will
keep pops around for the areas in the southeastern portions of the
state through the remains of the weekend until another larger trof
moves across the country bringing more widespread rain and thunder
for Sunday night into Monday. Signif differences between the ECMWF
and the GFS with the GFS being weaker with the boundary and leaving
a more stationary focus for prolonged showers...whereas the ECMWF is
more progressive and dries out the region on Tuesday.   At this
point, the ECMWF builds a weak upper ridge into the Midwest and the
GFS stays more active.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES






000
FXUS63 KLOT 281937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER


FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER


FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER


FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER


FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
123 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
123 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
123 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
123 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
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000
FXUS63 KLOT 281805
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
105 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281805
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
105 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 281735
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1235 PM CDT Thu Aug 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT THU AUG 28 2014

Morning surface analysis shows a warm front extending from
northern Missouri into the Ohio River Valley. A vigorous
upper-level low evident on water vapor imagery over western
Kansas/Nebraska has triggered a large complex of showers/thunder
north of the front across Iowa. This precip area is lifting
northeastward and will remain W/NW of the KILX CWA. Further
southeast along the front, only isolated showers are currently
observed across central Illinois. Showers/thunder will become more
numerous as the day progresses, but due to lack of strong upper
support, areal coverage will remain scattered in nature. Due to
clouds and precip, temperatures will be a bit cooler than in
previous days. Afternoon highs will range from around 80 far
northwest to the upper 80s south of I-70. Current forecast is
right on track, so no update is needed at this time.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 303 AM CDT THU AUG 28 2014

The location of the cold front appears to be just south of our
forecast area. It is forecast to return north as a warm front,
moving from SW to NE tonight. The unstable air mass extends well
north of the front all across our counties, as evidenced by the
isolated showers popping up early this morning across the northern
half of central IL. Added sprinkles to the northern counties for the
pre-dawn hours, and may need to extend the sprinkles after 12z east
toward CMI/DNV if the channel of precip continues. Otherwise,
overall thoughts on showers/storms are for a progression of chance
PoPs from west to east as the warm front begins to approach W-SW IL
in response to low pressure lifting from Nebraska into Minnesota.
The high res HRRR, ARW, and NMM along with the Canadian GEM all are
very scarce with coverage of storms over the next 12-24 hours, and
mainly in our far W-SW counties this afternoon. The 00z NAM, GFS,
and ECMWF all are a bit more aggressive, bringing precip as far east
as I-57 and LWV/Robinson. We kept the previous trends in the grids
of diurnally driven coverage, with higher chance PoPs in the SW half
of our forecast area this afternoon into early evening, then
trimming them back west later this evening/overnight. Confidence is
still low on precip coverage and timing based on very weak triggers
expected in our area northeast of the frontal boundary.

Sunshine will be filtered by mid-high clouds today, with highs in
the lower 80s north and some upper 80s S of Jacksonville to LWV.
Lows tonight will remain mainly in the lower 70s as the approaching
warm front keeps some cloud cover and higher dew points in our
area.

&&

.LONG TERM...(Friday through Wednesday)
ISSUED AT 303 AM CDT THU AUG 28 2014

Upper wave across the Rockies to make slow progress eastward
while dampening out Friday night over the Mississippi Valley.
Showers and storms Friday afternoon should be more scattered, with
a larger area of rain and storms coming in Friday night ahead of
the cold front. Have increased PoP`s to around 60% from I-55 west
by late Friday night and area-wide on Saturday.

The frontal boundary starts to become more diffuse Saturday night as
the upper wave flattens, and is difficult to discern by Sunday
morning. Have lingered the likely PoP`s across the southeast CWA
Saturday night as moisture continues to surge into the Ohio Valley,
and will keep high chance PoP`s going there into Sunday as well.
Further northwest, mainly dry conditions are on tap on Sunday.

Digging wave across the Rockies on Saturday night will be tracking
through the Mississippi Valley by Monday. Latest ECMWF draws some
cooler weather further south than the GFS, although not quite this
far south, as the west-east ridge across the lower tier of states
starts to strengthen again. Reasonable model agreement exists with
the associated cold front passing through on Monday, then hanging up
just south of I-70 as it becomes parallel to the upper flow. Showers
and storms to start moving back in Sunday night with the highest
chances on Monday. With the front hanging up, have lingered the
PoP`s across the southern CWA into Tuesday night, but did dry out
areas north as a small surface high drifts into the Great Lakes.

Rather muggy conditions to continue into early next week, with drier
air settling southward beginning Monday night behind the second
front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...BARNES







000
FXUS63 KILX 281735
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1235 PM CDT Thu Aug 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT THU AUG 28 2014

Morning surface analysis shows a warm front extending from
northern Missouri into the Ohio River Valley. A vigorous
upper-level low evident on water vapor imagery over western
Kansas/Nebraska has triggered a large complex of showers/thunder
north of the front across Iowa. This precip area is lifting
northeastward and will remain W/NW of the KILX CWA. Further
southeast along the front, only isolated showers are currently
observed across central Illinois. Showers/thunder will become more
numerous as the day progresses, but due to lack of strong upper
support, areal coverage will remain scattered in nature. Due to
clouds and precip, temperatures will be a bit cooler than in
previous days. Afternoon highs will range from around 80 far
northwest to the upper 80s south of I-70. Current forecast is
right on track, so no update is needed at this time.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 303 AM CDT THU AUG 28 2014

The location of the cold front appears to be just south of our
forecast area. It is forecast to return north as a warm front,
moving from SW to NE tonight. The unstable air mass extends well
north of the front all across our counties, as evidenced by the
isolated showers popping up early this morning across the northern
half of central IL. Added sprinkles to the northern counties for the
pre-dawn hours, and may need to extend the sprinkles after 12z east
toward CMI/DNV if the channel of precip continues. Otherwise,
overall thoughts on showers/storms are for a progression of chance
PoPs from west to east as the warm front begins to approach W-SW IL
in response to low pressure lifting from Nebraska into Minnesota.
The high res HRRR, ARW, and NMM along with the Canadian GEM all are
very scarce with coverage of storms over the next 12-24 hours, and
mainly in our far W-SW counties this afternoon. The 00z NAM, GFS,
and ECMWF all are a bit more aggressive, bringing precip as far east
as I-57 and LWV/Robinson. We kept the previous trends in the grids
of diurnally driven coverage, with higher chance PoPs in the SW half
of our forecast area this afternoon into early evening, then
trimming them back west later this evening/overnight. Confidence is
still low on precip coverage and timing based on very weak triggers
expected in our area northeast of the frontal boundary.

Sunshine will be filtered by mid-high clouds today, with highs in
the lower 80s north and some upper 80s S of Jacksonville to LWV.
Lows tonight will remain mainly in the lower 70s as the approaching
warm front keeps some cloud cover and higher dew points in our
area.

&&

.LONG TERM...(Friday through Wednesday)
ISSUED AT 303 AM CDT THU AUG 28 2014

Upper wave across the Rockies to make slow progress eastward
while dampening out Friday night over the Mississippi Valley.
Showers and storms Friday afternoon should be more scattered, with
a larger area of rain and storms coming in Friday night ahead of
the cold front. Have increased PoP`s to around 60% from I-55 west
by late Friday night and area-wide on Saturday.

The frontal boundary starts to become more diffuse Saturday night as
the upper wave flattens, and is difficult to discern by Sunday
morning. Have lingered the likely PoP`s across the southeast CWA
Saturday night as moisture continues to surge into the Ohio Valley,
and will keep high chance PoP`s going there into Sunday as well.
Further northwest, mainly dry conditions are on tap on Sunday.

Digging wave across the Rockies on Saturday night will be tracking
through the Mississippi Valley by Monday. Latest ECMWF draws some
cooler weather further south than the GFS, although not quite this
far south, as the west-east ridge across the lower tier of states
starts to strengthen again. Reasonable model agreement exists with
the associated cold front passing through on Monday, then hanging up
just south of I-70 as it becomes parallel to the upper flow. Showers
and storms to start moving back in Sunday night with the highest
chances on Monday. With the front hanging up, have lingered the
PoP`s across the southern CWA into Tuesday night, but did dry out
areas north as a small surface high drifts into the Great Lakes.

Rather muggy conditions to continue into early next week, with drier
air settling southward beginning Monday night behind the second
front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...BARNES







000
FXUS63 KILX 281735
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1235 PM CDT Thu Aug 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT THU AUG 28 2014

Morning surface analysis shows a warm front extending from
northern Missouri into the Ohio River Valley. A vigorous
upper-level low evident on water vapor imagery over western
Kansas/Nebraska has triggered a large complex of showers/thunder
north of the front across Iowa. This precip area is lifting
northeastward and will remain W/NW of the KILX CWA. Further
southeast along the front, only isolated showers are currently
observed across central Illinois. Showers/thunder will become more
numerous as the day progresses, but due to lack of strong upper
support, areal coverage will remain scattered in nature. Due to
clouds and precip, temperatures will be a bit cooler than in
previous days. Afternoon highs will range from around 80 far
northwest to the upper 80s south of I-70. Current forecast is
right on track, so no update is needed at this time.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 303 AM CDT THU AUG 28 2014

The location of the cold front appears to be just south of our
forecast area. It is forecast to return north as a warm front,
moving from SW to NE tonight. The unstable air mass extends well
north of the front all across our counties, as evidenced by the
isolated showers popping up early this morning across the northern
half of central IL. Added sprinkles to the northern counties for the
pre-dawn hours, and may need to extend the sprinkles after 12z east
toward CMI/DNV if the channel of precip continues. Otherwise,
overall thoughts on showers/storms are for a progression of chance
PoPs from west to east as the warm front begins to approach W-SW IL
in response to low pressure lifting from Nebraska into Minnesota.
The high res HRRR, ARW, and NMM along with the Canadian GEM all are
very scarce with coverage of storms over the next 12-24 hours, and
mainly in our far W-SW counties this afternoon. The 00z NAM, GFS,
and ECMWF all are a bit more aggressive, bringing precip as far east
as I-57 and LWV/Robinson. We kept the previous trends in the grids
of diurnally driven coverage, with higher chance PoPs in the SW half
of our forecast area this afternoon into early evening, then
trimming them back west later this evening/overnight. Confidence is
still low on precip coverage and timing based on very weak triggers
expected in our area northeast of the frontal boundary.

Sunshine will be filtered by mid-high clouds today, with highs in
the lower 80s north and some upper 80s S of Jacksonville to LWV.
Lows tonight will remain mainly in the lower 70s as the approaching
warm front keeps some cloud cover and higher dew points in our
area.

&&

.LONG TERM...(Friday through Wednesday)
ISSUED AT 303 AM CDT THU AUG 28 2014

Upper wave across the Rockies to make slow progress eastward
while dampening out Friday night over the Mississippi Valley.
Showers and storms Friday afternoon should be more scattered, with
a larger area of rain and storms coming in Friday night ahead of
the cold front. Have increased PoP`s to around 60% from I-55 west
by late Friday night and area-wide on Saturday.

The frontal boundary starts to become more diffuse Saturday night as
the upper wave flattens, and is difficult to discern by Sunday
morning. Have lingered the likely PoP`s across the southeast CWA
Saturday night as moisture continues to surge into the Ohio Valley,
and will keep high chance PoP`s going there into Sunday as well.
Further northwest, mainly dry conditions are on tap on Sunday.

Digging wave across the Rockies on Saturday night will be tracking
through the Mississippi Valley by Monday. Latest ECMWF draws some
cooler weather further south than the GFS, although not quite this
far south, as the west-east ridge across the lower tier of states
starts to strengthen again. Reasonable model agreement exists with
the associated cold front passing through on Monday, then hanging up
just south of I-70 as it becomes parallel to the upper flow. Showers
and storms to start moving back in Sunday night with the highest
chances on Monday. With the front hanging up, have lingered the
PoP`s across the southern CWA into Tuesday night, but did dry out
areas north as a small surface high drifts into the Great Lakes.

Rather muggy conditions to continue into early next week, with drier
air settling southward beginning Monday night behind the second
front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...BARNES







000
FXUS63 KILX 281735
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1235 PM CDT Thu Aug 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT THU AUG 28 2014

Morning surface analysis shows a warm front extending from
northern Missouri into the Ohio River Valley. A vigorous
upper-level low evident on water vapor imagery over western
Kansas/Nebraska has triggered a large complex of showers/thunder
north of the front across Iowa. This precip area is lifting
northeastward and will remain W/NW of the KILX CWA. Further
southeast along the front, only isolated showers are currently
observed across central Illinois. Showers/thunder will become more
numerous as the day progresses, but due to lack of strong upper
support, areal coverage will remain scattered in nature. Due to
clouds and precip, temperatures will be a bit cooler than in
previous days. Afternoon highs will range from around 80 far
northwest to the upper 80s south of I-70. Current forecast is
right on track, so no update is needed at this time.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 303 AM CDT THU AUG 28 2014

The location of the cold front appears to be just south of our
forecast area. It is forecast to return north as a warm front,
moving from SW to NE tonight. The unstable air mass extends well
north of the front all across our counties, as evidenced by the
isolated showers popping up early this morning across the northern
half of central IL. Added sprinkles to the northern counties for the
pre-dawn hours, and may need to extend the sprinkles after 12z east
toward CMI/DNV if the channel of precip continues. Otherwise,
overall thoughts on showers/storms are for a progression of chance
PoPs from west to east as the warm front begins to approach W-SW IL
in response to low pressure lifting from Nebraska into Minnesota.
The high res HRRR, ARW, and NMM along with the Canadian GEM all are
very scarce with coverage of storms over the next 12-24 hours, and
mainly in our far W-SW counties this afternoon. The 00z NAM, GFS,
and ECMWF all are a bit more aggressive, bringing precip as far east
as I-57 and LWV/Robinson. We kept the previous trends in the grids
of diurnally driven coverage, with higher chance PoPs in the SW half
of our forecast area this afternoon into early evening, then
trimming them back west later this evening/overnight. Confidence is
still low on precip coverage and timing based on very weak triggers
expected in our area northeast of the frontal boundary.

Sunshine will be filtered by mid-high clouds today, with highs in
the lower 80s north and some upper 80s S of Jacksonville to LWV.
Lows tonight will remain mainly in the lower 70s as the approaching
warm front keeps some cloud cover and higher dew points in our
area.

&&

.LONG TERM...(Friday through Wednesday)
ISSUED AT 303 AM CDT THU AUG 28 2014

Upper wave across the Rockies to make slow progress eastward
while dampening out Friday night over the Mississippi Valley.
Showers and storms Friday afternoon should be more scattered, with
a larger area of rain and storms coming in Friday night ahead of
the cold front. Have increased PoP`s to around 60% from I-55 west
by late Friday night and area-wide on Saturday.

The frontal boundary starts to become more diffuse Saturday night as
the upper wave flattens, and is difficult to discern by Sunday
morning. Have lingered the likely PoP`s across the southeast CWA
Saturday night as moisture continues to surge into the Ohio Valley,
and will keep high chance PoP`s going there into Sunday as well.
Further northwest, mainly dry conditions are on tap on Sunday.

Digging wave across the Rockies on Saturday night will be tracking
through the Mississippi Valley by Monday. Latest ECMWF draws some
cooler weather further south than the GFS, although not quite this
far south, as the west-east ridge across the lower tier of states
starts to strengthen again. Reasonable model agreement exists with
the associated cold front passing through on Monday, then hanging up
just south of I-70 as it becomes parallel to the upper flow. Showers
and storms to start moving back in Sunday night with the highest
chances on Monday. With the front hanging up, have lingered the
PoP`s across the southern CWA into Tuesday night, but did dry out
areas north as a small surface high drifts into the Great Lakes.

Rather muggy conditions to continue into early next week, with drier
air settling southward beginning Monday night behind the second
front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1235 PM CDT THU AUG 28 2014

Warm front currently across southern Illinois will be the main
weather-maker over the next 24 hours. 17z radar imagery continues
to show dry conditions across the KILX CWA, although scattered
showers/thunder are beginning to develop further south across
western Kentucky/far southern Illinois. This is shown quite nicely
by the 3-hr HRRR forecast, which also shows widely scattered
thunder developing further north into west-central Illinois after
20/21z. Will continue to feature a period of VCTS this afternoon
into the early evening before any diurnal convection dissipates.
Even after the afternoon showers fade away, forecast soundings are
showing mid-level cloud deck remaining in place tonight. This
should mitigate any potential fog development, with the Rapid
Refresh showing visbys at or above 6sm through 10z. Winds will be
from the E/SE at less than 10kt this afternoon and tonight, then
will become S/SE by Friday morning as the warm front lifts
northward.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BARNES
SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...BARNES







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