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000
FXUS63 KILX 020155
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
855 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 855 PM CDT SAT AUG 1 2015

A BROAD TROUGH OVER THE EASTERN U.S. WITH NORTHWESTERLY FLOW ALOFT
OVER CENTRAL ILLINOIS...A SHORTWAVE TO THE NORTHWEST WILL BRING
CHANCES OF THUNDERSTORMS DEVELOPING WEST OF THE ILLINOIS RIVER BY
EARLY MORNING...SPREADING EASTWARD ACROSS AREAS FROM AROUND I-72
NORTHWARD THROUGH THE DAY. MODELS SUGGESTING CONVECTION WILL
DEVELOP OVER SOUTHERN MN/IOWA THE NEXT FEW HOURS...PROPAGATING ESE
OVERNIGHT...WHILE CONVECTION ONGOING OVER NORTHERN MISSOURI WILL
WEAKEN AND MOVE SOUTHEAST OVERNIGHT. PREDOMINANT MODEL SOLUTIONS
PROPAGATE STRONGER CONVECTION ACROSS THE GREAT LAKES WITH STRONGER
UPPER LEVEL FORCING...LEAVING WEAKENING CONVECTIVE REMNANTS
MOVING INTO CENTRAL IL EARLY IN THE MORNING. WITH MODEST AMOUNTS
OF MOISTURE CHARACTERIZED BY DEWPOINTS IN THE 60S...EXPECTING LOWS
TO REACH THE MID-UPPER 60S TONIGHT. CURRENT FORECAST DEPICTS THE
SITUATION WELL AND NO SIGNIFICANT UPDATES PLANNED THIS EVENING.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 615 PM CDT SAT AUG 1 2015

PREDOMINANTLY VFR CONDITIONS EXPECTED THROUGH THE 00Z TAF PERIOD.
LATEST MODEL GUIDANCE GENERALLY CONSISTENT WITH DRY CONDITIONS FOR
CENTRAL IL TERMINALS UNTIL 17Z...THEN BRINGING A CHANCE FOR
THUNDERSTORMS MAINLY FOR NORTHERN TERMINALS KPIA-KBMI. SEVERAL
CLUSTERS OF CONVECTION EXPECTED TO DEVELOP TO THE WEST...THEN
EITHER WEAKEN OR MOVE PAST CENTRAL IL TO THE NORTH MID-MORNING
THROUGH AFTERNOON SUNDAY...SO CHANCES FOR DISRUPTION OF VFR
CONDITIONS ARE MINIMAL AND HAVE ONLY INCLUDED VCTS AT TERMINALS
KPIA-KBMI AFTER 17Z. WINDS SW THROUGH THE PERIOD...4-7 KTS
OVERNIGHT...INCREASING TO 12-16 KTS AFTER 17Z WITH GUSTS AROUND 20
KTS POSSIBLE IN THE AFTERNOON.


&&

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

$$

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



000
FXUS63 KILX 020155
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
855 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 855 PM CDT SAT AUG 1 2015

A BROAD TROUGH OVER THE EASTERN U.S. WITH NORTHWESTERLY FLOW ALOFT
OVER CENTRAL ILLINOIS...A SHORTWAVE TO THE NORTHWEST WILL BRING
CHANCES OF THUNDERSTORMS DEVELOPING WEST OF THE ILLINOIS RIVER BY
EARLY MORNING...SPREADING EASTWARD ACROSS AREAS FROM AROUND I-72
NORTHWARD THROUGH THE DAY. MODELS SUGGESTING CONVECTION WILL
DEVELOP OVER SOUTHERN MN/IOWA THE NEXT FEW HOURS...PROPAGATING ESE
OVERNIGHT...WHILE CONVECTION ONGOING OVER NORTHERN MISSOURI WILL
WEAKEN AND MOVE SOUTHEAST OVERNIGHT. PREDOMINANT MODEL SOLUTIONS
PROPAGATE STRONGER CONVECTION ACROSS THE GREAT LAKES WITH STRONGER
UPPER LEVEL FORCING...LEAVING WEAKENING CONVECTIVE REMNANTS
MOVING INTO CENTRAL IL EARLY IN THE MORNING. WITH MODEST AMOUNTS
OF MOISTURE CHARACTERIZED BY DEWPOINTS IN THE 60S...EXPECTING LOWS
TO REACH THE MID-UPPER 60S TONIGHT. CURRENT FORECAST DEPICTS THE
SITUATION WELL AND NO SIGNIFICANT UPDATES PLANNED THIS EVENING.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 615 PM CDT SAT AUG 1 2015

PREDOMINANTLY VFR CONDITIONS EXPECTED THROUGH THE 00Z TAF PERIOD.
LATEST MODEL GUIDANCE GENERALLY CONSISTENT WITH DRY CONDITIONS FOR
CENTRAL IL TERMINALS UNTIL 17Z...THEN BRINGING A CHANCE FOR
THUNDERSTORMS MAINLY FOR NORTHERN TERMINALS KPIA-KBMI. SEVERAL
CLUSTERS OF CONVECTION EXPECTED TO DEVELOP TO THE WEST...THEN
EITHER WEAKEN OR MOVE PAST CENTRAL IL TO THE NORTH MID-MORNING
THROUGH AFTERNOON SUNDAY...SO CHANCES FOR DISRUPTION OF VFR
CONDITIONS ARE MINIMAL AND HAVE ONLY INCLUDED VCTS AT TERMINALS
KPIA-KBMI AFTER 17Z. WINDS SW THROUGH THE PERIOD...4-7 KTS
OVERNIGHT...INCREASING TO 12-16 KTS AFTER 17Z WITH GUSTS AROUND 20
KTS POSSIBLE IN THE AFTERNOON.


&&

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

$$

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



  [top]

000
FXUS63 KLOT 012346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST TO POSSIBLY SOUTH-SOUTHWEST WINDS ON SUNDAY AFTERNOON
  AT SUSTAINED SPEEDS TO 20 KT AND GUSTS TO 30-35 KT.

* SCATTERED LIKELY WEAKENING SHRA/TSRA IN THE REGION SUNDAY
  MORNING.

* LIKELY TSRA DURING SUNDAY EVENING.


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

A FEW EARLIER CONVECTIVE CELLS IN NORTHWEST IL HAVE WEAKENED AS
CONVERGENCE HAS WANED AND HAVING NOW PASSED PEAK HEATING. GUSTS
WILL CONTINUE TO FALL OFF THROUGH 01Z-02Z. SO A QUIET NIGHT
EXPECTED AT LOCAL TERMINALS OUTSIDE OF 30-40 KT FLOW DEVELOPING
LATE TONIGHT BETWEEN 1000-2000 FT...WITH THE HIGHER END SPEEDS
NEAR RFD POSSIBLY BRINGING LLWS.

SCATTERED STORMS ARE EXPECTED TO DEVELOP ACROSS MN...WI...AND
POSSIBLY PARTS OF IA TONIGHT AND MOVE SOUTHEAST. DUE TO LACK OF A
STRONG UPPER DISTURBANCE AND A MARGINAL FOCUS OF THE LOW-LEVEL
JET...A WELL-DEFINED MESOSCALE CONVECTIVE SYSTEM /MCS/ IS NOT
EXPECTED TO DEVELOP UPSTREAM OF THE AREA. HOWEVER...SCATTERED
SHRA/TSRA...LIKELY IN A WEAKENING STATE...ARE POSSIBLE DURING THE
MORNING HOURS AFTER SUNRISE SO HAVE CONTINUED THAT MENTION IN THE
TAFS.

SUNDAY AFTERNOON CONTINUES TO LOOK LIKE A TIME WITH LIMITED FOCUS
FOR CONVECTIVE REDEVELOPMENT ACROSS NORTHERN IL AND NORTHWEST
IN. THE BOUNDARY LAYER IS PRESENTLY FORECAST TO MIX SUFFICIENTLY
WITHIN A TIGHTENING PRESSURE GRADIENT TO BRING SUSTAINED SPEEDS
AROUND 20 KT AND GUSTS AT OR EXCEEDING 30 KT...POSSIBLY REACHING
35 KT. THE DIRECTION COULD GO AS FAR BACKED AS 210 DEGREES...AT
LEAST SPORADICALLY AT ORD AND MDW.

THE SYSTEM COOL FRONT IS EXPECTED TO PROGRESS SOUTHEAST THROUGH
WISCONSIN LATE IN THE DAY SUNDAY AND THEN ACROSS THE TERMINALS
DURING THE MID-LATE EVENING. THERE SHOULD BE CONVECTIVE
DEVELOPMENT ALONG THIS OVER WI WITH POTENTIAL MCS DEVELOPMENT OR
AT LEAST A CORRIDOR OF CONVECTION MOVING SOUTHEAST. SO HAVE
MENTIONED THUNDER FOR A COUPLE HOUR WINDOW IN THE EXTENDED
PORTION OF THE ORD TAF.


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

* MEDIUM-HIGH IN WIND GUSTS EXCEEDING 30 KT. LOW-MEDIUM IN START
  TIME AND DURATION OF WINDS.

* MEDIUM IN WIND DIRECTION REMAINING 220-230 DURING PEAK WINDS.

* LOW IN TSRA CHANCES IN THE MORNING.

* MEDIUM-HIGH IN TSRA CHANCES DURING THE EVENING. LOW-MEDIUM IN
  TIMING.


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

MONDAY-TUESDAY...VFR. MAINLY NORTHWEST WINDS.
WEDNESDAY...VFR. NORTHEAST WINDS.
THURSDAY-FRIDAY...CHANCE OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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000
FXUS63 KLOT 012346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST TO POSSIBLY SOUTH-SOUTHWEST WINDS ON SUNDAY AFTERNOON
  AT SUSTAINED SPEEDS TO 20 KT AND GUSTS TO 30-35 KT.

* SCATTERED LIKELY WEAKENING SHRA/TSRA IN THE REGION SUNDAY
  MORNING.

* LIKELY TSRA DURING SUNDAY EVENING.


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

A FEW EARLIER CONVECTIVE CELLS IN NORTHWEST IL HAVE WEAKENED AS
CONVERGENCE HAS WANED AND HAVING NOW PASSED PEAK HEATING. GUSTS
WILL CONTINUE TO FALL OFF THROUGH 01Z-02Z. SO A QUIET NIGHT
EXPECTED AT LOCAL TERMINALS OUTSIDE OF 30-40 KT FLOW DEVELOPING
LATE TONIGHT BETWEEN 1000-2000 FT...WITH THE HIGHER END SPEEDS
NEAR RFD POSSIBLY BRINGING LLWS.

SCATTERED STORMS ARE EXPECTED TO DEVELOP ACROSS MN...WI...AND
POSSIBLY PARTS OF IA TONIGHT AND MOVE SOUTHEAST. DUE TO LACK OF A
STRONG UPPER DISTURBANCE AND A MARGINAL FOCUS OF THE LOW-LEVEL
JET...A WELL-DEFINED MESOSCALE CONVECTIVE SYSTEM /MCS/ IS NOT
EXPECTED TO DEVELOP UPSTREAM OF THE AREA. HOWEVER...SCATTERED
SHRA/TSRA...LIKELY IN A WEAKENING STATE...ARE POSSIBLE DURING THE
MORNING HOURS AFTER SUNRISE SO HAVE CONTINUED THAT MENTION IN THE
TAFS.

SUNDAY AFTERNOON CONTINUES TO LOOK LIKE A TIME WITH LIMITED FOCUS
FOR CONVECTIVE REDEVELOPMENT ACROSS NORTHERN IL AND NORTHWEST
IN. THE BOUNDARY LAYER IS PRESENTLY FORECAST TO MIX SUFFICIENTLY
WITHIN A TIGHTENING PRESSURE GRADIENT TO BRING SUSTAINED SPEEDS
AROUND 20 KT AND GUSTS AT OR EXCEEDING 30 KT...POSSIBLY REACHING
35 KT. THE DIRECTION COULD GO AS FAR BACKED AS 210 DEGREES...AT
LEAST SPORADICALLY AT ORD AND MDW.

THE SYSTEM COOL FRONT IS EXPECTED TO PROGRESS SOUTHEAST THROUGH
WISCONSIN LATE IN THE DAY SUNDAY AND THEN ACROSS THE TERMINALS
DURING THE MID-LATE EVENING. THERE SHOULD BE CONVECTIVE
DEVELOPMENT ALONG THIS OVER WI WITH POTENTIAL MCS DEVELOPMENT OR
AT LEAST A CORRIDOR OF CONVECTION MOVING SOUTHEAST. SO HAVE
MENTIONED THUNDER FOR A COUPLE HOUR WINDOW IN THE EXTENDED
PORTION OF THE ORD TAF.


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

* MEDIUM-HIGH IN WIND GUSTS EXCEEDING 30 KT. LOW-MEDIUM IN START
  TIME AND DURATION OF WINDS.

* MEDIUM IN WIND DIRECTION REMAINING 220-230 DURING PEAK WINDS.

* LOW IN TSRA CHANCES IN THE MORNING.

* MEDIUM-HIGH IN TSRA CHANCES DURING THE EVENING. LOW-MEDIUM IN
  TIMING.


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

MONDAY-TUESDAY...VFR. MAINLY NORTHWEST WINDS.
WEDNESDAY...VFR. NORTHEAST WINDS.
THURSDAY-FRIDAY...CHANCE OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST TO POSSIBLY SOUTH-SOUTHWEST WINDS ON SUNDAY AFTERNOON
  AT SUSTAINED SPEEDS TO 20 KT AND GUSTS TO 30-35 KT.

* SCATTERED LIKELY WEAKENING SHRA/TSRA IN THE REGION SUNDAY
  MORNING.

* LIKELY TSRA DURING SUNDAY EVENING.


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

A FEW EARLIER CONVECTIVE CELLS IN NORTHWEST IL HAVE WEAKENED AS
CONVERGENCE HAS WANED AND HAVING NOW PASSED PEAK HEATING. GUSTS
WILL CONTINUE TO FALL OFF THROUGH 01Z-02Z. SO A QUIET NIGHT
EXPECTED AT LOCAL TERMINALS OUTSIDE OF 30-40 KT FLOW DEVELOPING
LATE TONIGHT BETWEEN 1000-2000 FT...WITH THE HIGHER END SPEEDS
NEAR RFD POSSIBLY BRINGING LLWS.

SCATTERED STORMS ARE EXPECTED TO DEVELOP ACROSS MN...WI...AND
POSSIBLY PARTS OF IA TONIGHT AND MOVE SOUTHEAST. DUE TO LACK OF A
STRONG UPPER DISTURBANCE AND A MARGINAL FOCUS OF THE LOW-LEVEL
JET...A WELL-DEFINED MESOSCALE CONVECTIVE SYSTEM /MCS/ IS NOT
EXPECTED TO DEVELOP UPSTREAM OF THE AREA. HOWEVER...SCATTERED
SHRA/TSRA...LIKELY IN A WEAKENING STATE...ARE POSSIBLE DURING THE
MORNING HOURS AFTER SUNRISE SO HAVE CONTINUED THAT MENTION IN THE
TAFS.

SUNDAY AFTERNOON CONTINUES TO LOOK LIKE A TIME WITH LIMITED FOCUS
FOR CONVECTIVE REDEVELOPMENT ACROSS NORTHERN IL AND NORTHWEST
IN. THE BOUNDARY LAYER IS PRESENTLY FORECAST TO MIX SUFFICIENTLY
WITHIN A TIGHTENING PRESSURE GRADIENT TO BRING SUSTAINED SPEEDS
AROUND 20 KT AND GUSTS AT OR EXCEEDING 30 KT...POSSIBLY REACHING
35 KT. THE DIRECTION COULD GO AS FAR BACKED AS 210 DEGREES...AT
LEAST SPORADICALLY AT ORD AND MDW.

THE SYSTEM COOL FRONT IS EXPECTED TO PROGRESS SOUTHEAST THROUGH
WISCONSIN LATE IN THE DAY SUNDAY AND THEN ACROSS THE TERMINALS
DURING THE MID-LATE EVENING. THERE SHOULD BE CONVECTIVE
DEVELOPMENT ALONG THIS OVER WI WITH POTENTIAL MCS DEVELOPMENT OR
AT LEAST A CORRIDOR OF CONVECTION MOVING SOUTHEAST. SO HAVE
MENTIONED THUNDER FOR A COUPLE HOUR WINDOW IN THE EXTENDED
PORTION OF THE ORD TAF.


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

* MEDIUM-HIGH IN WIND GUSTS EXCEEDING 30 KT. LOW-MEDIUM IN START
  TIME AND DURATION OF WINDS.

* MEDIUM IN WIND DIRECTION REMAINING 220-230 DURING PEAK WINDS.

* LOW IN TSRA CHANCES IN THE MORNING.

* MEDIUM-HIGH IN TSRA CHANCES DURING THE EVENING. LOW-MEDIUM IN
  TIMING.


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

MONDAY-TUESDAY...VFR. MAINLY NORTHWEST WINDS.
WEDNESDAY...VFR. NORTHEAST WINDS.
THURSDAY-FRIDAY...CHANCE OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 012346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST TO POSSIBLY SOUTH-SOUTHWEST WINDS ON SUNDAY AFTERNOON
  AT SUSTAINED SPEEDS TO 20 KT AND GUSTS TO 30-35 KT.

* SCATTERED LIKELY WEAKENING SHRA/TSRA IN THE REGION SUNDAY
  MORNING.

* LIKELY TSRA DURING SUNDAY EVENING.


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

A FEW EARLIER CONVECTIVE CELLS IN NORTHWEST IL HAVE WEAKENED AS
CONVERGENCE HAS WANED AND HAVING NOW PASSED PEAK HEATING. GUSTS
WILL CONTINUE TO FALL OFF THROUGH 01Z-02Z. SO A QUIET NIGHT
EXPECTED AT LOCAL TERMINALS OUTSIDE OF 30-40 KT FLOW DEVELOPING
LATE TONIGHT BETWEEN 1000-2000 FT...WITH THE HIGHER END SPEEDS
NEAR RFD POSSIBLY BRINGING LLWS.

SCATTERED STORMS ARE EXPECTED TO DEVELOP ACROSS MN...WI...AND
POSSIBLY PARTS OF IA TONIGHT AND MOVE SOUTHEAST. DUE TO LACK OF A
STRONG UPPER DISTURBANCE AND A MARGINAL FOCUS OF THE LOW-LEVEL
JET...A WELL-DEFINED MESOSCALE CONVECTIVE SYSTEM /MCS/ IS NOT
EXPECTED TO DEVELOP UPSTREAM OF THE AREA. HOWEVER...SCATTERED
SHRA/TSRA...LIKELY IN A WEAKENING STATE...ARE POSSIBLE DURING THE
MORNING HOURS AFTER SUNRISE SO HAVE CONTINUED THAT MENTION IN THE
TAFS.

SUNDAY AFTERNOON CONTINUES TO LOOK LIKE A TIME WITH LIMITED FOCUS
FOR CONVECTIVE REDEVELOPMENT ACROSS NORTHERN IL AND NORTHWEST
IN. THE BOUNDARY LAYER IS PRESENTLY FORECAST TO MIX SUFFICIENTLY
WITHIN A TIGHTENING PRESSURE GRADIENT TO BRING SUSTAINED SPEEDS
AROUND 20 KT AND GUSTS AT OR EXCEEDING 30 KT...POSSIBLY REACHING
35 KT. THE DIRECTION COULD GO AS FAR BACKED AS 210 DEGREES...AT
LEAST SPORADICALLY AT ORD AND MDW.

THE SYSTEM COOL FRONT IS EXPECTED TO PROGRESS SOUTHEAST THROUGH
WISCONSIN LATE IN THE DAY SUNDAY AND THEN ACROSS THE TERMINALS
DURING THE MID-LATE EVENING. THERE SHOULD BE CONVECTIVE
DEVELOPMENT ALONG THIS OVER WI WITH POTENTIAL MCS DEVELOPMENT OR
AT LEAST A CORRIDOR OF CONVECTION MOVING SOUTHEAST. SO HAVE
MENTIONED THUNDER FOR A COUPLE HOUR WINDOW IN THE EXTENDED
PORTION OF THE ORD TAF.


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

* MEDIUM-HIGH IN WIND GUSTS EXCEEDING 30 KT. LOW-MEDIUM IN START
  TIME AND DURATION OF WINDS.

* MEDIUM IN WIND DIRECTION REMAINING 220-230 DURING PEAK WINDS.

* LOW IN TSRA CHANCES IN THE MORNING.

* MEDIUM-HIGH IN TSRA CHANCES DURING THE EVENING. LOW-MEDIUM IN
  TIMING.


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

MONDAY-TUESDAY...VFR. MAINLY NORTHWEST WINDS.
WEDNESDAY...VFR. NORTHEAST WINDS.
THURSDAY-FRIDAY...CHANCE OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 012346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST TO POSSIBLY SOUTH-SOUTHWEST WINDS ON SUNDAY AFTERNOON
  AT SUSTAINED SPEEDS TO 20 KT AND GUSTS TO 30-35 KT.

* SCATTERED LIKELY WEAKENING SHRA/TSRA IN THE REGION SUNDAY
  MORNING.

* LIKELY TSRA DURING SUNDAY EVENING.


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

A FEW EARLIER CONVECTIVE CELLS IN NORTHWEST IL HAVE WEAKENED AS
CONVERGENCE HAS WANED AND HAVING NOW PASSED PEAK HEATING. GUSTS
WILL CONTINUE TO FALL OFF THROUGH 01Z-02Z. SO A QUIET NIGHT
EXPECTED AT LOCAL TERMINALS OUTSIDE OF 30-40 KT FLOW DEVELOPING
LATE TONIGHT BETWEEN 1000-2000 FT...WITH THE HIGHER END SPEEDS
NEAR RFD POSSIBLY BRINGING LLWS.

SCATTERED STORMS ARE EXPECTED TO DEVELOP ACROSS MN...WI...AND
POSSIBLY PARTS OF IA TONIGHT AND MOVE SOUTHEAST. DUE TO LACK OF A
STRONG UPPER DISTURBANCE AND A MARGINAL FOCUS OF THE LOW-LEVEL
JET...A WELL-DEFINED MESOSCALE CONVECTIVE SYSTEM /MCS/ IS NOT
EXPECTED TO DEVELOP UPSTREAM OF THE AREA. HOWEVER...SCATTERED
SHRA/TSRA...LIKELY IN A WEAKENING STATE...ARE POSSIBLE DURING THE
MORNING HOURS AFTER SUNRISE SO HAVE CONTINUED THAT MENTION IN THE
TAFS.

SUNDAY AFTERNOON CONTINUES TO LOOK LIKE A TIME WITH LIMITED FOCUS
FOR CONVECTIVE REDEVELOPMENT ACROSS NORTHERN IL AND NORTHWEST
IN. THE BOUNDARY LAYER IS PRESENTLY FORECAST TO MIX SUFFICIENTLY
WITHIN A TIGHTENING PRESSURE GRADIENT TO BRING SUSTAINED SPEEDS
AROUND 20 KT AND GUSTS AT OR EXCEEDING 30 KT...POSSIBLY REACHING
35 KT. THE DIRECTION COULD GO AS FAR BACKED AS 210 DEGREES...AT
LEAST SPORADICALLY AT ORD AND MDW.

THE SYSTEM COOL FRONT IS EXPECTED TO PROGRESS SOUTHEAST THROUGH
WISCONSIN LATE IN THE DAY SUNDAY AND THEN ACROSS THE TERMINALS
DURING THE MID-LATE EVENING. THERE SHOULD BE CONVECTIVE
DEVELOPMENT ALONG THIS OVER WI WITH POTENTIAL MCS DEVELOPMENT OR
AT LEAST A CORRIDOR OF CONVECTION MOVING SOUTHEAST. SO HAVE
MENTIONED THUNDER FOR A COUPLE HOUR WINDOW IN THE EXTENDED
PORTION OF THE ORD TAF.


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

* MEDIUM-HIGH IN WIND GUSTS EXCEEDING 30 KT. LOW-MEDIUM IN START
  TIME AND DURATION OF WINDS.

* MEDIUM IN WIND DIRECTION REMAINING 220-230 DURING PEAK WINDS.

* LOW IN TSRA CHANCES IN THE MORNING.

* MEDIUM-HIGH IN TSRA CHANCES DURING THE EVENING. LOW-MEDIUM IN
  TIMING.


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

MONDAY-TUESDAY...VFR. MAINLY NORTHWEST WINDS.
WEDNESDAY...VFR. NORTHEAST WINDS.
THURSDAY-FRIDAY...CHANCE OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 012346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST TO POSSIBLY SOUTH-SOUTHWEST WINDS ON SUNDAY AFTERNOON
  AT SUSTAINED SPEEDS TO 20 KT AND GUSTS TO 30-35 KT.

* SCATTERED LIKELY WEAKENING SHRA/TSRA IN THE REGION SUNDAY
  MORNING.

* LIKELY TSRA DURING SUNDAY EVENING.


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

A FEW EARLIER CONVECTIVE CELLS IN NORTHWEST IL HAVE WEAKENED AS
CONVERGENCE HAS WANED AND HAVING NOW PASSED PEAK HEATING. GUSTS
WILL CONTINUE TO FALL OFF THROUGH 01Z-02Z. SO A QUIET NIGHT
EXPECTED AT LOCAL TERMINALS OUTSIDE OF 30-40 KT FLOW DEVELOPING
LATE TONIGHT BETWEEN 1000-2000 FT...WITH THE HIGHER END SPEEDS
NEAR RFD POSSIBLY BRINGING LLWS.

SCATTERED STORMS ARE EXPECTED TO DEVELOP ACROSS MN...WI...AND
POSSIBLY PARTS OF IA TONIGHT AND MOVE SOUTHEAST. DUE TO LACK OF A
STRONG UPPER DISTURBANCE AND A MARGINAL FOCUS OF THE LOW-LEVEL
JET...A WELL-DEFINED MESOSCALE CONVECTIVE SYSTEM /MCS/ IS NOT
EXPECTED TO DEVELOP UPSTREAM OF THE AREA. HOWEVER...SCATTERED
SHRA/TSRA...LIKELY IN A WEAKENING STATE...ARE POSSIBLE DURING THE
MORNING HOURS AFTER SUNRISE SO HAVE CONTINUED THAT MENTION IN THE
TAFS.

SUNDAY AFTERNOON CONTINUES TO LOOK LIKE A TIME WITH LIMITED FOCUS
FOR CONVECTIVE REDEVELOPMENT ACROSS NORTHERN IL AND NORTHWEST
IN. THE BOUNDARY LAYER IS PRESENTLY FORECAST TO MIX SUFFICIENTLY
WITHIN A TIGHTENING PRESSURE GRADIENT TO BRING SUSTAINED SPEEDS
AROUND 20 KT AND GUSTS AT OR EXCEEDING 30 KT...POSSIBLY REACHING
35 KT. THE DIRECTION COULD GO AS FAR BACKED AS 210 DEGREES...AT
LEAST SPORADICALLY AT ORD AND MDW.

THE SYSTEM COOL FRONT IS EXPECTED TO PROGRESS SOUTHEAST THROUGH
WISCONSIN LATE IN THE DAY SUNDAY AND THEN ACROSS THE TERMINALS
DURING THE MID-LATE EVENING. THERE SHOULD BE CONVECTIVE
DEVELOPMENT ALONG THIS OVER WI WITH POTENTIAL MCS DEVELOPMENT OR
AT LEAST A CORRIDOR OF CONVECTION MOVING SOUTHEAST. SO HAVE
MENTIONED THUNDER FOR A COUPLE HOUR WINDOW IN THE EXTENDED
PORTION OF THE ORD TAF.


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

* MEDIUM-HIGH IN WIND GUSTS EXCEEDING 30 KT. LOW-MEDIUM IN START
  TIME AND DURATION OF WINDS.

* MEDIUM IN WIND DIRECTION REMAINING 220-230 DURING PEAK WINDS.

* LOW IN TSRA CHANCES IN THE MORNING.

* MEDIUM-HIGH IN TSRA CHANCES DURING THE EVENING. LOW-MEDIUM IN
  TIMING.


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

MONDAY-TUESDAY...VFR. MAINLY NORTHWEST WINDS.
WEDNESDAY...VFR. NORTHEAST WINDS.
THURSDAY-FRIDAY...CHANCE OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KILX 012314
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
614 PM CDT SAT AUG 1 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 615 PM CDT SAT AUG 1 2015

PREDOMINANTLY VFR CONDITIONS EXPECTED THROUGH THE 00Z TAF PERIOD.
LATEST MODEL GUIDANCE GENERALLY CONSISTENT WITH DRY CONDITIONS FOR
CENTRAL IL TERMINALS UNTIL 17Z...THEN BRINGING A CHANCE FOR
THUNDERSTORMS MAINLY FOR NORTHERN TERMINALS KPIA-KBMI. SEVERAL
CLUSTERS OF CONVECTION EXPECTED TO DEVELOP TO THE WEST...THEN
EITHER WEAKEN OR MOVE PAST CENTRAL IL TO THE NORTH MID-MORNING
THROUGH AFTERNOON SUNDAY...SO CHANCES FOR DISRUPTION OF VFR
CONDITIONS ARE MINIMAL AND HAVE ONLY INCLUDED VCTS AT TERMINALS
KPIA-KBMI AFTER 17Z. WINDS SW THROUGH THE PERIOD...4-7 KTS
OVERNIGHT...INCREASING TO 12-16 KTS AFTER 17Z WITH GUSTS AROUND 20
KTS POSSIBLE IN THE AFTERNOON.

&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...ONTON



000
FXUS63 KILX 012314
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
614 PM CDT SAT AUG 1 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 615 PM CDT SAT AUG 1 2015

PREDOMINANTLY VFR CONDITIONS EXPECTED THROUGH THE 00Z TAF PERIOD.
LATEST MODEL GUIDANCE GENERALLY CONSISTENT WITH DRY CONDITIONS FOR
CENTRAL IL TERMINALS UNTIL 17Z...THEN BRINGING A CHANCE FOR
THUNDERSTORMS MAINLY FOR NORTHERN TERMINALS KPIA-KBMI. SEVERAL
CLUSTERS OF CONVECTION EXPECTED TO DEVELOP TO THE WEST...THEN
EITHER WEAKEN OR MOVE PAST CENTRAL IL TO THE NORTH MID-MORNING
THROUGH AFTERNOON SUNDAY...SO CHANCES FOR DISRUPTION OF VFR
CONDITIONS ARE MINIMAL AND HAVE ONLY INCLUDED VCTS AT TERMINALS
KPIA-KBMI AFTER 17Z. WINDS SW THROUGH THE PERIOD...4-7 KTS
OVERNIGHT...INCREASING TO 12-16 KTS AFTER 17Z WITH GUSTS AROUND 20
KTS POSSIBLE IN THE AFTERNOON.

&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...ONTON




000
FXUS63 KLOT 012141
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
441 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST WINDS ON SUNDAY INCREASING WITH GUSTS UP TO 25-30KT.

* CHANCE FOR SHRA/TSRA SUNDAY AND SUNDAY EVENING...WITH THE BETTER
  LIKELIHOOD APPEARING IN THE MORNING AND THEN AGAIN DURING THE
  EVENING.

KREIN/MTF


//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN


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

* HIGH IN WINDS.

* LOW IN TIMING/COVERAGE/DURATION OF TSRA IMPACTING THE TERMINALS
  SUNDAY MORNING.

KREIN/MTF


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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012141
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
441 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST WINDS ON SUNDAY INCREASING WITH GUSTS UP TO 25-30KT.

* CHANCE FOR SHRA/TSRA SUNDAY AND SUNDAY EVENING...WITH THE BETTER
  LIKELIHOOD APPEARING IN THE MORNING AND THEN AGAIN DURING THE
  EVENING.

KREIN/MTF


//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN


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

* HIGH IN WINDS.

* LOW IN TIMING/COVERAGE/DURATION OF TSRA IMPACTING THE TERMINALS
  SUNDAY MORNING.

KREIN/MTF


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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012141
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
441 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST WINDS ON SUNDAY INCREASING WITH GUSTS UP TO 25-30KT.

* CHANCE FOR SHRA/TSRA SUNDAY AND SUNDAY EVENING...WITH THE BETTER
  LIKELIHOOD APPEARING IN THE MORNING AND THEN AGAIN DURING THE
  EVENING.

KREIN/MTF


//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN


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

* HIGH IN WINDS.

* LOW IN TIMING/COVERAGE/DURATION OF TSRA IMPACTING THE TERMINALS
  SUNDAY MORNING.

KREIN/MTF


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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012141
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
441 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STRENGTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORESEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* SOUTHWEST WINDS ON SUNDAY INCREASING WITH GUSTS UP TO 25-30KT.

* CHANCE FOR SHRA/TSRA SUNDAY AND SUNDAY EVENING...WITH THE BETTER
  LIKELIHOOD APPEARING IN THE MORNING AND THEN AGAIN DURING THE
  EVENING.

KREIN/MTF


//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN


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

* HIGH IN WINDS.

* LOW IN TIMING/COVERAGE/DURATION OF TSRA IMPACTING THE TERMINALS
  SUNDAY MORNING.

KREIN/MTF


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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012041
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
341 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STREGNTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORSEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 012041
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
341 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STREGNTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORSEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES. IF MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS
CONCEIVABLE THAT BETTER SEVERE THREAT WOULD FOCUS INTO FAR
NORTHERN ILLINOIS COUNTIES. ALSO...FASTER STORM MOTIONS COULD
PRECLUDE MUCH OF A FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012026
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
326 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STREGNTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORSEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES AND EVEN AN ISOLATED TORNADO THREAT/POSSIBLY WITH QLCS. IF
MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS CONCEIVABLE THAT
BETTER SEVERE THREAT WOULD FOCUS INTO FAR NORTHERN ILLINOIS
COUNTIES. ALSO...FASTER STORM MOTIONS COULD PRECLUDE MUCH OF A
FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KLOT 012026
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
326 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STREGNTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORSEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES AND EVEN AN ISOLATED TORNADO THREAT/POSSIBLY WITH QLCS. IF
MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS CONCEIVABLE THAT
BETTER SEVERE THREAT WOULD FOCUS INTO FAR NORTHERN ILLINOIS
COUNTIES. ALSO...FASTER STORM MOTIONS COULD PRECLUDE MUCH OF A
FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 012026
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
326 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STREGNTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORSEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES AND EVEN AN ISOLATED TORNADO THREAT/POSSIBLY WITH QLCS. IF
MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS CONCEIVABLE THAT
BETTER SEVERE THREAT WOULD FOCUS INTO FAR NORTHERN ILLINOIS
COUNTIES. ALSO...FASTER STORM MOTIONS COULD PRECLUDE MUCH OF A
FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 012026
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
326 PM CDT SAT AUG 1 2015

.SHORT TERM...
325 PM CDT

THROUGH SUNDAY EVENING...

MAIN FORECAST CONCERNS ARE WITH THE POTENTIAL FOR SEVERE STORMS
LATE SUNDAY INTO SUNDAY EVENING...AS WELL AS STRONG GUSTY WINDS
OUTSIDE OF ANY THUNDERSTORMS.

LATE THIS AFTERNOON INTO EARLY EVENING...WEAK UPPER LEVEL
DISTURBANCE WILL BE OVER THE REGION. SEVERAL MODELS AND HI-RES
NEAR TERM GUIDANCE HAS BEEN INSISTENT ON BREAKING OUT ISOLATED
SHOWERS. HOWEVER...RECENT AIRCRAFT SOUNDINGS SHOW VERY DRY LOW
LEVELS AND CUMULUS FIELD OVER PORTIONS OVER THE REGION DOESNT
APPEAR VERY ROBUST. CANNOT COMPLETELY RULE OUT A VERY ISOLATED
SHOWER OVER NORTHERN IL OR NW IN...BUT HAVE LEFT OUT MENTION OF
ANY PRECIP. ATTENTION WILL THEN TURN TO CONVECTION/POSSIBLE
LOOSELY ORGANIZED MCS FROM NW WI TO EASTERN NE OVERNIGHT AND ITS
EVOLUTION. ASSOCIATED SHORTWAVE WILL APPROACH THE AREA BY EARLY
SUNDAY. WEAKENING STORMS COULD TRY TO SNEAK INTO FAR NORTHERN
ILLINOIS TOWARD DAYBREAK. CORFIDI VECTORS ARE WEST TO EAST...SO
ITS UNCERTAIN HOW EFFECTIVE PROPAGATION INTO CWA WILL BE INTO
SUNDAY MORNING. LOW LEVEL JET WILL INCREASE LATE AND ADVECTION OF
STEEP MIDLEVEL LAPSE RATES WILL INCREASE MUCAPE...THOUGH IT DOES
NOT APPEAR ANYTHING OTHER THAN A STRONG STORM OR TWO IS FAVORED TO
SURVIVE INTO NORTHERN IL. HAVE TAILORED POPS TO MID CHANCE NORTH
OF INTERSTATE 80 AND LOW CHANCE TO SLIGHT MOVING SOUTH FROM THERE.

WILL NEED TO WATCH FOR ANY OUTFLOW BOUNDARIES THAT COULD KICK OFF
ISOLATED STORMS FROM MID DAY INTO THE EARLY-MID
AFTERNOON...ALTHOUGH OVERALL FORCING IS LACKING DURING THIS TIME.
SYNOPTICALLY...EXPANSIVE HIGH PRESSURE WILL SINK SOUTHEAST AND
STREGNTHENING COLD FRONTAL TROUGH WILL BE APPROACHING FROM
NORTHWEST. PRESSURE FALLS/TIGHTENING GRADIENT WILL RESULT IN
STRONG SOUTHWEST WINDS GUSTING UP TO 35 MPH...WITH SOUNDINGS
INDICATING SOME POTENTIAL FOR OCCASIONAL GUSTS TO 40 MPH.
ALOFT...A VERY STRONG EML WILL BE ADVECTED EASTWARD...WITH STEEP
NEARLY DRY ADIABATIC MIDLEVEL LAPSE RATES. ASSUMING A PERIOD OF
NEARLY FULL SUN...THERMAL PROGS SUPPORT HIGHS REACHING AT LEAST
UPPER 80S-LOWER 90S AND GUSTY SOUTHWEST LOW LEVEL FLOW WILL RETURN
DEWPOINTS INTO THE 60S TO AROUND 70. STEEP MIDLEVEL LAPSE RATES
AND WARM/HUMID AIRMASS WILL YIELD MODERATE TO STRONGLY UNSTABLE
AIRMASS BUT EML COULD ALSO YIELD A STRONG CAP...WITH MAIN SHORT
WAVE FORCING STILL OFF TO NORTH CLOSER TO THE COLD FRONT. IF THERE
IS AN UNFORSEEN SUBTLE SHORTWAVE TO BREACH THE CAPPING DURING
AFTERNOON...ANY STORM THAT GOES IN ENVIRONMENT WITH PLENTY OF
INSTABILITY...40-45 KT OF DEEP LAYER SHEAR AND IMPRESSIVE LOWER
LEVEL WIND FIELDS COULD BECOME SEVERE.

WITH THIS BEING SAID...HAVE STAYED CONSERVATIVE WITH POPS UNTIL
BETTER FORCING ARRIVES AND MODELS ARE IN DECENT AGREEMENT IN
DEVELOPING A LINEAR MCS ACROSS WISCONSIN AND PROPAGATING IT
SOUTHEASTWARD. MAIN QUESTION IS TIMING OF THIS POTENTIAL MCS AND
WHETHER SOME DIURNAL WEAKENING WILL OCCUR WITH SOUTHEASTWARD
EXTENT. DID BRING LIKELY POPS ALONG NORTHERN TIER OF COUNTIES IN
EARLY EVENING SOUTHWARD TO CHICAGO AND POINTS WEST AND SOUTH
DURING MID EVENING HOURS...THOUGH COLD POOL FORMATION COULD AID IN
QUICKER PROPAGATION AS SHOWN BY SOME HI-RES GUIDANCE SUCH AS 12Z
4KM NAM. 40-50 KT OF 0-3 KM BULK SHEAR AND AFOREMENTIONED
IMPRESSIVE LOWER LEVEL WIND FIELD WOULD YIELD A DAMAGING WIND
THREAT...THOUGH CANNOT RULE OUT LARGE HAIL CONSIDERING STEEP LAPSE
RATES AND EVEN AN ISOLATED TORNADO THREAT/POSSIBLY WITH QLCS. IF
MCS IS SLOWER TO PROPAGATE INTO CWA...THEN ITS CONCEIVABLE THAT
BETTER SEVERE THREAT WOULD FOCUS INTO FAR NORTHERN ILLINOIS
COUNTIES. ALSO...FASTER STORM MOTIONS COULD PRECLUDE MUCH OF A
FLOODING RISK.

RC

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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




000
FXUS63 KILX 012016
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
316 PM CDT SAT AUG 1 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

&&

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1237 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
LATEST MODEL GUIDANCE SUGGESTS CONVECTION THAT DEVELOPS ACROSS THE
CENTRAL/NORTHERN PLAINS LATER THIS AFTERNOON/EVENING MAY REMAIN
WELL N/NW OF CENTRAL ILLINOIS OVERNIGHT INTO SUNDAY MORNING. AS
SUCH...HAVE MAINTAINED A DRY FORECAST AT THE TERMINALS WITH ONLY
BKN HIGH CLOUDS. WINDS WILL BE LIGHT/VARIABLE ACROSS THE EASTERN
HALF OF THE AREA THIS AFTERNOON...THEN WILL BECOME SW AT AROUND
5KT ACROSS THE BOARD TONIGHT.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...BARNES



000
FXUS63 KILX 012016
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
316 PM CDT SAT AUG 1 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

&&

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1237 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
LATEST MODEL GUIDANCE SUGGESTS CONVECTION THAT DEVELOPS ACROSS THE
CENTRAL/NORTHERN PLAINS LATER THIS AFTERNOON/EVENING MAY REMAIN
WELL N/NW OF CENTRAL ILLINOIS OVERNIGHT INTO SUNDAY MORNING. AS
SUCH...HAVE MAINTAINED A DRY FORECAST AT THE TERMINALS WITH ONLY
BKN HIGH CLOUDS. WINDS WILL BE LIGHT/VARIABLE ACROSS THE EASTERN
HALF OF THE AREA THIS AFTERNOON...THEN WILL BECOME SW AT AROUND
5KT ACROSS THE BOARD TONIGHT.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...BARNES




000
FXUS63 KLOT 011949
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
249 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 011949
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
249 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
248 PM CDT

LATE SUNDAY NIGHT THROUGH SATURDAY...

PERIOD WILL BEGIN WITH SHOWER/THUNDERSTORM ACTIVITY LIKELY
EXITING TO THE EAST WITH EASTWARD MOVING SURFACE TROUGH/FRONTAL
BOUNDARY. DID LEAVE CHANCE POPS ACROSS EAST CENTRAL ILLINOIS AND
NORTHWEST INDIANA WITH SLIGHT CHANCE ACROSS PORTIONS OF NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. HOWEVER...THERE IS THE
POTENTIAL FOR ANY THUNDERSTORM DEVELOPMENT TO DEPART THE AREA
SLIGHTLY SOONER...ESPECIALLY IF A LINE OF CONVECTION WERE TO
DEVELOP. AFTER THIS POTENTIAL FOR PRECIP...EARLY NEXT WEEK APPEARS
TO BE ON THE DRIER SIDE...AND HAVE REMOVED POPS DURING THIS TIME.
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE AREA AS LARGE SCALE
PATTERN WILL BE DICTATED BY LARGE UPPER LEVEL CENTER SLOWLY
DROPPING SOUTHEAST THROUGH SOUTHERN CANADA. WITH ANY STRONGER MID
LEVEL FEATURES REMAINING TO THE NORTH AND TO THE SOUTHWEST OF THE
AREA...PRECIP DEVELOPMENT WILL STAY OUTSIDE OF THE CWA.
HOWEVER...THIS WILL PROVIDE COOLER AND DRIER CONDITIONS WITH
INITIALLY NORMAL HIGH TEMPS IN THE LOW 80S LIKELY ON MONDAY...BUT
WITH A TREND TOWARDS BELOW NORMAL HIGH TEMPS IN THE 70S BY MID
WEEK. GUIDANCE IN FAIR AGREEMENT WITH TAKING THIS UPPER LEVEL LOW
TO THE EAST LATER IN THE WORK WEEK...WITH BETTER POTENTIAL FOR
UPSTREAM ENERGY AND PRECIP TO WORK ITS WAY TOWARDS THE AREA.

RODRIGUEZ

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
248 PM CDT

WESTERLY WINDS IN PLACE TODAY AS LOW PRESSURE REMAINS TO THE
NORTH AND WHILE HIGH PRESSURE IS SITUATED OVER THE SOUTHERN PLAINS
TO THE MID MISSISSIPPI VALLEY. EXPECT WINDS TO BECOME MORE
SOUTHWEST THROUGH THE AFTERNOON AND INTO THE EVENING...WITH SPEEDS
THEN EXPECTED TO INCREASE THROUGH THE NIGHT. SOUTHWEST WINDS WILL
THEN REALLY INCREASE ON SUNDAY WITH THE APPROACH OF A SEPARATE
SYSTEM AND WITH THE HIGHEST WINDS/GUSTS LIKELY FROM LATE SUNDAY
MORNING THROUGH EARLY SUNDAY EVENING. HAVE INCREASED WINDS DURING
THIS TIME FRAME TO 30KT FOR BOTH THE NEARSHORE AND OPEN
WATERS...BUT PRIMARILY FOR THE SOUTHERN HALF. THERE IS SOME
POTENTIAL FOR OCCASIONAL GALE FORCE GUSTS IN THE AFTERNOON...BUT
THIS WILL BE MAINLY FOR THE NEARSHORE WATERS. WINDS WILL DIMINISH
SUNDAY NIGHT INTO MONDAY...WHILE THEY TURN MORE WEST/NORTHWEST.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...9 AM SUNDAY TO 10 PM SUNDAY.

&&

$$

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

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



000
FXUS63 KLOT 011921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
221 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 011921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
221 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WSWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  VEERING BACK TO WNWLY THROUGH THE AFTERNOON. GUSTINESS SUBSIDING
  AT SUNSET.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KILX 011737
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1237 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 1019 AM CDT SAT AUG 1 2015

NO CHANGES NEEDED TO THE GOING FORECAST...AS ANOTHER WARM/DRY
SUMMER DAY IS UNFOLDING ACROSS CENTRAL ILLINOIS. 15Z/10AM TEMPS
ARE ALREADY IN THE UPPER 70S AND LOWER 80S...WELL ON THE WAY TO
AFTERNOON HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1237 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
LATEST MODEL GUIDANCE SUGGESTS CONVECTION THAT DEVELOPS ACROSS THE
CENTRAL/NORTHERN PLAINS LATER THIS AFTERNOON/EVENING MAY REMAIN
WELL N/NW OF CENTRAL ILLINOIS OVERNIGHT INTO SUNDAY MORNING. AS
SUCH...HAVE MAINTAINED A DRY FORECAST AT THE TERMINALS WITH ONLY
BKN HIGH CLOUDS. WINDS WILL BE LIGHT/VARIABLE ACROSS THE EASTERN
HALF OF THE AREA THIS AFTERNOON...THEN WILL BECOME SW AT AROUND
5KT ACROSS THE BOARD TONIGHT.

&&

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

$$

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




000
FXUS63 KILX 011737
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1237 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 1019 AM CDT SAT AUG 1 2015

NO CHANGES NEEDED TO THE GOING FORECAST...AS ANOTHER WARM/DRY
SUMMER DAY IS UNFOLDING ACROSS CENTRAL ILLINOIS. 15Z/10AM TEMPS
ARE ALREADY IN THE UPPER 70S AND LOWER 80S...WELL ON THE WAY TO
AFTERNOON HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1237 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
LATEST MODEL GUIDANCE SUGGESTS CONVECTION THAT DEVELOPS ACROSS THE
CENTRAL/NORTHERN PLAINS LATER THIS AFTERNOON/EVENING MAY REMAIN
WELL N/NW OF CENTRAL ILLINOIS OVERNIGHT INTO SUNDAY MORNING. AS
SUCH...HAVE MAINTAINED A DRY FORECAST AT THE TERMINALS WITH ONLY
BKN HIGH CLOUDS. WINDS WILL BE LIGHT/VARIABLE ACROSS THE EASTERN
HALF OF THE AREA THIS AFTERNOON...THEN WILL BECOME SW AT AROUND
5KT ACROSS THE BOARD TONIGHT.

&&

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

$$

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




000
FXUS63 KILX 011737
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1237 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 1019 AM CDT SAT AUG 1 2015

NO CHANGES NEEDED TO THE GOING FORECAST...AS ANOTHER WARM/DRY
SUMMER DAY IS UNFOLDING ACROSS CENTRAL ILLINOIS. 15Z/10AM TEMPS
ARE ALREADY IN THE UPPER 70S AND LOWER 80S...WELL ON THE WAY TO
AFTERNOON HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1237 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
LATEST MODEL GUIDANCE SUGGESTS CONVECTION THAT DEVELOPS ACROSS THE
CENTRAL/NORTHERN PLAINS LATER THIS AFTERNOON/EVENING MAY REMAIN
WELL N/NW OF CENTRAL ILLINOIS OVERNIGHT INTO SUNDAY MORNING. AS
SUCH...HAVE MAINTAINED A DRY FORECAST AT THE TERMINALS WITH ONLY
BKN HIGH CLOUDS. WINDS WILL BE LIGHT/VARIABLE ACROSS THE EASTERN
HALF OF THE AREA THIS AFTERNOON...THEN WILL BECOME SW AT AROUND
5KT ACROSS THE BOARD TONIGHT.

&&

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

$$

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




000
FXUS63 KILX 011737
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1237 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 1019 AM CDT SAT AUG 1 2015

NO CHANGES NEEDED TO THE GOING FORECAST...AS ANOTHER WARM/DRY
SUMMER DAY IS UNFOLDING ACROSS CENTRAL ILLINOIS. 15Z/10AM TEMPS
ARE ALREADY IN THE UPPER 70S AND LOWER 80S...WELL ON THE WAY TO
AFTERNOON HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1237 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
LATEST MODEL GUIDANCE SUGGESTS CONVECTION THAT DEVELOPS ACROSS THE
CENTRAL/NORTHERN PLAINS LATER THIS AFTERNOON/EVENING MAY REMAIN
WELL N/NW OF CENTRAL ILLINOIS OVERNIGHT INTO SUNDAY MORNING. AS
SUCH...HAVE MAINTAINED A DRY FORECAST AT THE TERMINALS WITH ONLY
BKN HIGH CLOUDS. WINDS WILL BE LIGHT/VARIABLE ACROSS THE EASTERN
HALF OF THE AREA THIS AFTERNOON...THEN WILL BECOME SW AT AROUND
5KT ACROSS THE BOARD TONIGHT.

&&

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

$$

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




000
FXUS63 KLOT 011733
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1233 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  THROUGH THIS AFTERNOON.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 011733
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1233 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  THROUGH THIS AFTERNOON.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 011733
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1233 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  THROUGH THIS AFTERNOON.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 011733
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1233 PM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT
  THROUGH THIS AFTERNOON.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING AND INCREASING 15-20KT
  SUSTAINED WITH GUSTS UP TO 25-30KT.

* ANOTHER CHANCE FOR THUNDERSTORMS SUNDAY EVENING.

KREIN

//DISCUSSION...UPDATED 18Z...

STRENGTHENING WLY-WNWLY WINDS ARE INCREASING ACROSS THE REGION AS
DEEP LOW PRESSURE SITS OVER HUDSON BAY AND HIGH PRESSURE SETTLES
INTO THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. A VERY WEAK MID
LEVEL IMPULSE MOVING THROUGH THE FAST NWLY FLOW ALOFT HAS
GENERATED SOME MID CLOUD WITH BASES ARND 8KFT AND A FEW ISOLD
SHRA. HOWEVER...WHAT LITTLE MID LEVEL FORCING THERE IS ASSOCIATED
WITH THE WEAK IMPULSE WILL REMAIN NORTHEAST OF THE TERMINALS AND
NO PCPN IS EXPECTED. THE REMAINDER OF THE NIGHT SHOULD BE QUIET
WITH WINDS DIMINISHING TO ARND 10KT AT SUNSET.

THE NEXT CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE
AREA TOMORROW. THERE IS STILL SOME SPREAD IN THE FORECAST MODEL
SOLUTIONS FOR THE EXACT TIMING OF TS OVER NRN IL/IN.  HOWEVER...
THE GENERAL IDEA IS FOR A STRONGER MID LEVEL IMPULSE TO CROSS NRN
IL/IN TOMORROW MORNING WHICH SHOULD GENERATE SOME SHOWERS AND
THUNDERSTORMS. THE MAIN ISSUE IS TIMING. SOME GUIDANCE IS
SUGGESTING THAT THE PREFERRED TIMING WILL BE DURG THE EARLY
MORNING HOURS WHILE OTHER MODELS FAVOR A SLOWER SOLUTION WITH THE
HIGHER TS POTENTIAL DURG THE LATE MORNING HOURS. GIVEN THE TIMING
UNCERTAINTY AT THIS POINT...WILL MAINTAIN THE TIMING OF THE GOING
FORECAST. THE REMAINDER OF SUNDAY ALSO HAS SOME UNCERTAINTY FOR
THE POTENTIAL FOR ADDITIONAL TS CHANCES THROUGH THE REMAINDER OF
THE DAY. STRONG SWLY FLOW AT 5KFT AND INCREASING SFC HEAT AND
HUMIDITY WILL BE CONDUCIVE TO TS DEVELOPMENT AHEAD OF A COLD
FRONT DROPPING SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. LATEST MODEL SOUNDINGS INDICATE THAT THERE
SHOULD BE AN ELEVATED INVERSION...WHICH COULD DELAY ANY TS UNTIL
THE FRONT ACTUALLY CROSSES THE AREA TOMORROW EVENING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 06Z SUNDAY.

* LOW CONFIDENCE IN TIMING/COVERAGE/DURATION OF TS IMPACTING THE
  TERMINALS SUNDAY MORNING.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 011605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1105 AM CDT SAT AUG 1 2015

.UPDATE...
1105 AM CDT

GOING FORECAST LARGELY IN GOOD SHAPE...AND JUST MADE TWEAKS TO
HOURLY TEMPERATURE...DEWPOINT AND SKY TRENDS. STILL EXPECTING
HIGHS IN THE MID 80S TO AROUND 90...HIGHEST IN THE CHICAGO HEAT
ISLAND AS HAS BEEN TYPICAL THE PAST WEEK. IN FACT...IF MIDWAY AND
THE MIDWAY COOP REACH 90 AGAIN TODAY...IT WILL BE THE 6TH
CONSECUTIVE 90 DEGREE DAY AT THOSE SITES. DEWPOINTS ARE TRYING TO
CREEP UP SOME TODAY...BUT DRY WEDGE ALOFT NOTED ON 12Z RAOBS
CONTINUING TO KEEP DEWPOINTS IN 50S TO LOW 60S. THUS ANOTHER DAY
OF WARM TEMPERATURES BUT COMFORTABLE HUMIDITY LEVELS FOR THE FIRST
DAY OF AUGUST.

W/V SHOWS WEAK DISTURBANCE OVER SOUTHERN WISCONSIN PRODUCING
MIDLEVEL CLOUD COVER OVER SOUTHERN WI AND PORTIONS OF NORTHERN IL.
TRAJECTORY OF ISOLATED SHOWER ACTIVITY OVER SOUTHERN WI FAVORS
THESE SHOWERS AT MOST CLIPPING FAR NORTHEAST ILLINOIS OVER THE
NEXT 1 TO POSSIBLY 2 HOURS...SO JUST HAVE SLIGHT CHANCE POPS IN
THAT AREA...WITH DRY CONDITIONS EXPECTED THE REST OF THE AFTERNOON
AND EVENING BEHIND THIS WAVE.

RC

&&

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

KREIN

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SATURDAY
  NIGHT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUNDAY.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 011547
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1047 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

KREIN

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SATURDAY
  NIGHT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUNDAY.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 011547
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1047 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WLY-WNWLY WINDS WITH SPEEDS ARND 10-12 KT AND GUSTS TO ARND 18KT.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

KREIN

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SATURDAY
  NIGHT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUNDAY.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KILX 011519
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1019 AM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 1019 AM CDT SAT AUG 1 2015

NO CHANGES NEEDED TO THE GOING FORECAST...AS ANOTHER WARM/DRY
SUMMER DAY IS UNFOLDING ACROSS CENTRAL ILLINOIS. 15Z/10AM TEMPS
ARE ALREADY IN THE UPPER 70S AND LOWER 80S...WELL ON THE WAY TO
AFTERNOON HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 630 AM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES NEXT 24HRS. SKIES
SHOULD BE CLEAR ACROSS THE SITES MOST OF THE DAY. THEN AS STORMS
DEVELOP WELL WEST OF THE AREA...COULD SEE SOME BLOW OFF CIRRUS
DRIFT OVER THE SITES DURING THE EVENING. AS THE STORMS MOVE EAST
TOWARD THE AREA...CLOUDS COULD THICKEN VERY LATE IN THE PERIOD
WITH SKIES BECOMING BROKEN AT AROUND 15KFT. WINDS WILL BE LIGHT
AND VARIABLE THIS MORNING BUT THEN BECOME SOUTHWESTERLY AS THE
HIGH PRESSURE MOVES SOUTHEAST OF THE AREA. WINDS SPEEDS ONCE THE
WINDS BECOME SOUTHWEST SHOULD BE LESS THAN 10KTS...EVEN DURING THE
AFTERNOON AND EVENING.


&&

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

$$

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




000
FXUS63 KLOT 011411
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
911 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS PERSIST WITH SPEEDS BECMG 10-12 KT AND GUSTS TO
  AROUND 18KT.

* BRIEF POCKET OF CIGS ARND 8KFT AGL MID-MORNING.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

KREIN

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SUN
  NGT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUN.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 011411
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
911 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS PERSIST WITH SPEEDS BECMG 10-12 KT AND GUSTS TO
  AROUND 18KT.

* BRIEF POCKET OF CIGS ARND 8KFT AGL MID-MORNING.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

KREIN

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SUN
  NGT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUN.

KREIN

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 011142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS PERSIST WITH SPEEDS BETWEEN 7-10KT...GUSTS DEVELOP
  MID-MORNING TO AROUND 20KT.

* BRIEF POCKET OF CIGS ARND 8KFT AGL MID-MORNING.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

BEACHLER

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20-24KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SUN
  NGT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUN.

BEACHLER

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 011142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS PERSIST WITH SPEEDS BETWEEN 7-10KT...GUSTS DEVELOP
  MID-MORNING TO AROUND 20KT.

* BRIEF POCKET OF CIGS ARND 8KFT AGL MID-MORNING.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

BEACHLER

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20-24KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SUN
  NGT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUN.

BEACHLER

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 011142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS PERSIST WITH SPEEDS BETWEEN 7-10KT...GUSTS DEVELOP
  MID-MORNING TO AROUND 20KT.

* BRIEF POCKET OF CIGS ARND 8KFT AGL MID-MORNING.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

BEACHLER

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20-24KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SUN
  NGT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUN.

BEACHLER

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 011142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS PERSIST WITH SPEEDS BETWEEN 7-10KT...GUSTS DEVELOP
  MID-MORNING TO AROUND 20KT.

* BRIEF POCKET OF CIGS ARND 8KFT AGL MID-MORNING.

* WINDS TURN SOUTHWEST EARLY SUNDAY MORNING...INCREASING CHANCES
  FOR THUNDERSTORMS AFTER DAYBREAK SUNDAY.

BEACHLER

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

HIGH PRESSURE REMAINS CENTERED ACROSS THE TENN VALLEY...ALLOWING
WINDS TO REMAIN WESTERLY AGAIN TODAY. MIXING IS EXPECTED TO
INCREASE AND ALLOW WINDS TO BECOME GUSTY AT TIMES...NEARING
20-24KT. EARLY THIS MORNING A POCKET OF LIGHT RAIN WAS SLIDING
SOUTHEAST ACROSS SOUTHEAST MINNESOTA/SOUTHWEST WISC...ALTHOUGH IT
APPEARS THIS AREA OF PRECIP WAS DISSIPATING AS IT MOVED INTO MUCH
DRIER AIR. SOME CLOUDS ARND 8KFT AGL WILL ARRIVE ASSOCIATED WITH
THE DECAYING SHOWERS LATER THIS MORNING...HOWEVER NOT EXPECTED TO
LOWER VFR CONDS.

HIGH PRESSURE DRIFTS EAST TONIGHT...WITH WINDS SLOWLY TURNING
SOUTHWESTERLY. A LOW PRESSURE WILL DEVELOP OVER THE PLAINS EARLY
SUNDAY...WITH AN AREA OF SHOWERS AND THUNDERSTORMS EXPECTED TO
DEVELOP WITH THIS LOW. THE BEST TIMING TO ARRIVE ACROSS NORTHERN
IL/NORTHWEST IN DOES NOT APPEAR TO BE UNTIL AFTER DAYBREAK
SUN...AND MAY END UP BEING LATE MORNING SUNDAY. CONFIDENCE SEEMS
FAVORABLE FOR THUNDERSTORMS...SO HAVE GONE AHEAD AND MENTIONED A
PROB30 GROUP WITH THE CURRENT 30HR TAF AT ORD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH 00Z SUN.

* MEDIUM CONFIDENCE IN TAF SITES REMAINING DRY THRU LATE SUN
  NGT...THEN BEST TIMING FOR THUNDERSTORMS APPEARS TO BE AFTER
  DAYBREAK SUN.

BEACHLER

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

SUNDAY NIGHT...MAINLY VFR. CHANCE OF SHRA/TSRA EARLY IN THE
EVENING.

MONDAY...MAINLY VFR. NORTHWEST WINDS.

TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.

WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY AND FRIDAY...CHANCE OF SHRA. EAST WINDS.

BEACHLER

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KILX 011129
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
629 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 630 AM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES NEXT 24HRS. SKIES
SHOULD BE CLEAR ACROSS THE SITES MOST OF THE DAY. THEN AS STORMS
DEVELOP WELL WEST OF THE AREA...COULD SEE SOME BLOW OFF CIRRUS
DRIFT OVER THE SITES DURING THE EVENING. AS THE STORMS MOVE EAST
TOWARD THE AREA...CLOUDS COULD THICKEN VERY LATE IN THE PERIOD
WITH SKIES BECOMING BROKEN AT AROUND 15KFT. WINDS WILL BE LIGHT
AND VARIABLE THIS MORNING BUT THEN BECOME SOUTHWESTERLY AS THE
HIGH PRESSURE MOVES SOUTHEAST OF THE AREA. WINDS SPEEDS ONCE THE
WINDS BECOME SOUTHWEST SHOULD BE LESS THAN 10KTS...EVEN DURING THE
AFTERNOON AND EVENING.

&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KILX 011129
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
629 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 630 AM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES NEXT 24HRS. SKIES
SHOULD BE CLEAR ACROSS THE SITES MOST OF THE DAY. THEN AS STORMS
DEVELOP WELL WEST OF THE AREA...COULD SEE SOME BLOW OFF CIRRUS
DRIFT OVER THE SITES DURING THE EVENING. AS THE STORMS MOVE EAST
TOWARD THE AREA...CLOUDS COULD THICKEN VERY LATE IN THE PERIOD
WITH SKIES BECOMING BROKEN AT AROUND 15KFT. WINDS WILL BE LIGHT
AND VARIABLE THIS MORNING BUT THEN BECOME SOUTHWESTERLY AS THE
HIGH PRESSURE MOVES SOUTHEAST OF THE AREA. WINDS SPEEDS ONCE THE
WINDS BECOME SOUTHWEST SHOULD BE LESS THAN 10KTS...EVEN DURING THE
AFTERNOON AND EVENING.

&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 011129
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
629 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 630 AM CDT SAT AUG 1 2015

VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES NEXT 24HRS. SKIES
SHOULD BE CLEAR ACROSS THE SITES MOST OF THE DAY. THEN AS STORMS
DEVELOP WELL WEST OF THE AREA...COULD SEE SOME BLOW OFF CIRRUS
DRIFT OVER THE SITES DURING THE EVENING. AS THE STORMS MOVE EAST
TOWARD THE AREA...CLOUDS COULD THICKEN VERY LATE IN THE PERIOD
WITH SKIES BECOMING BROKEN AT AROUND 15KFT. WINDS WILL BE LIGHT
AND VARIABLE THIS MORNING BUT THEN BECOME SOUTHWESTERLY AS THE
HIGH PRESSURE MOVES SOUTHEAST OF THE AREA. WINDS SPEEDS ONCE THE
WINDS BECOME SOUTHWEST SHOULD BE LESS THAN 10KTS...EVEN DURING THE
AFTERNOON AND EVENING.

&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KLOT 010918
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
418 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 010918
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
418 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 010832
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 010832
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 010832
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 010832
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 AM CDT SAT AUG 1 2015

.SHORT TERM...
330 AM CDT

THROUGH SUNDAY...

THE MAIN FOCUS DURING THE SHORT TERM PERIOD WILL BE WITH REGARDS TO
CONVECTIVE CHANCES LATER TONIGHT THROUGH SUNDAY...WITH THE
POTENTIAL OF SEVERE STORMS...ESPECIALLY SUNDAY AFTERNOON/EVENING.

TODAY LOOKS TO BE ANOTHER WARM AND DRY DAY ACROSS THE REGION.
HOWEVER...THE CURRENT FORECAST HAS A SLIGHT CHANCE MENTION OF A
SHOWER OR TWO THIS MORNING OVER FAR NORTHERN ILLINOIS AND I HAVE
OPTED TO LEAVE THIS CHANCE GOING AS A WEAK DISTURBANCE SHIFTS EAST-
SOUTHEASTWARD ACROSS SOUTHERN WISCONSIN AND OVER SOUTHERN LAKE
MICHIGAN LATER THIS MORNING. REGIONAL RADAR IMAGERY INDICATES THAT A
FEW ISOLATED SHOWERS HAVE DEVELOPED OVER SOUTHEASTERN MINNESOTA...IN
ASSOCIATION WITH THIS DISTURBANCE. ANY SHOWERS THAT OCCUR WILL BE
SHORT LIVED AND SPOTTY IN COVERAGE...SO IT SHOULD NOT BE A BIG DEAL.
OTHERWISE...EXPECT TEMPERATURES TO AGAIN CLIMB INTO THE MID TO UPPER
80S AGAIN UNDER MAINLY SUNNY SKIES. DEWPOINTS WILL BEGIN A SLOW
INCREASE TODAY AS THE FLOW BEGINS TO SHIFT WEST-
SOUTHWESTERLY...THOUGH THE BETTER DEWPOINTS WILL LIKELY NOT GET HERE
UNTIL TONIGHT INTO SUNDAY.

A FAST NORTHWESTERLY UPPER LEVEL PATTERN WILL PERSIST ACROSS THE
CENTRAL CONUS THROUGH THE PERIOD. WITHIN THIS PATTERN...MID LEVEL
HEIGHT FALLS ASSOCIATED WITH A SHORT WAVE IMPULSE...CURRENTLY OVER
MONTANA...IS EXPECTED TO FOCUS/ENHANCE A VEERING WEST-SOUTHWESTERLY
LOW LEVEL JET ACROSS THE MID MISSOURI AND INTO THE UPPER MISSISSIPPI
VALLEYS TONIGHT. THIS SHOULD PROMOTE A FOCUS FOR THUNDERSTORMS TO
GROW UPSCALE INTO ONE OR TWO MCS`S OVER NORTHERN IOWA AND ADJACENT
PORTIONS OF SOUTHERN MINNESOTA AND WISCONSIN OVERNIGHT. THESE STORMS
WILL THEN LIKELY TREND TO THE EAST-SOUTHEAST TOWARDS NORTHERN
ILLINOIS BY EARLY SUNDAY MORNING. THE MAIN THREAT FROM THESE STORMS
WOULD BE STRONG GUSTY WINDS OVER FAR NORTHERN ILLINOIS.
HOWEVER...THESE STORMS COULD END UP COMING ACROSS NORTHERN ILLINOIS
EARLY SUNDAY MORNING IN A WEAKENING PHASE...SO THE EXTENT OF ANY
STRONG TO SEVERE STORMS WITH THIS FIRST WAVE IS UNCERTAIN.

THIS INITIAL WAVE OF REMNANT STORMS IS EXPECTED TO DISSIPATE AND
SHIFT OUT OF THE AREA BY MIDDAY SUNDAY. ATTENTION THEN TURNS TO
ANOTHER SIGNIFICANT DISTURBANCE EXPECTED TO DIG SOUTHEASTWARD OVER
THE UPPER GREAT LAKES REGION DURING THE DAY SUNDAY. STRONG HEIGHT
FALLS ASSOCIATED WITH THIS DISTURBANCE WILL LIKELY STRENGTHEN A
SURFACE COLD FRONTAL TROUGH OVER THE GREAT LAKES REGION AND DRIVE
IT SOUTHWARD OVER THE REGION BY SUNDAY EVENING. THE PREFRONTAL
AIRMASS LOOKS TO BECOME QUITE UNSTABLE ACROSS THE AREA AS STEEP
MID-LEVEL LAPSE RATES ASSOCIATED WITH AN EML GET ADVECTED EASTWARD
ATOP A VERY WARM AND MOIST BOUNDARY LAYER. ASSUMING THAT ANY
MORNING CLOUD COVER FROM REMNANT NOCTURNAL CONVECTION CLEARS
OFF...WHICH IT CURRENTLY APPEARS WILL BE THE CASE...TEMPERATURES
COULD WARM INTO THE UPPER 80S TO POSSIBLY LOW 90S...WITH DEW
POINTS LIKELY TO RECOVER BACK INTO THE MID TO UPPER 60S. THIS
WOULD SUGGEST THAT MLCAPE VALUES COULD GET IN EXCESS OF 2500 J/KG
BY SUNDAY AFTERNOON OVER THE AREA. SO...WITH THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES...ALONG WITH 30-35 KT OF BULK LAYER
SHEAR...THERE CERTAINLY APPEARS TO BE SOME POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS OVER THE AREA LATE SUNDAY AFTERNOON
AND INTO THE EVENING AS THE COLD FRONT SHIFTS OVER THE AREA. AT
THIS TIME...IT APPEARS THAT LARGE HAIL AND DAMAGING WINDS WOULD BE
THE MAIN THREATS WITH THESE POTENTIAL STORMS.

IT ALSO APPEARS THAT IT WILL BE A BIT ON THE WINDY SIDE OVER THE
AREA ON SUNDAY. WITH THE COLD FRONTAL TROUGH OF LOW PRESSURE
EXPECTED TO STRENGTHEN OVER WISCONSIN SUNDAY...THE PRESSURE GRADIENT
WILL STRENGTHEN...AND THIS LOOKS TO SUPPORT SOME HEALTHY
SOUTHWESTERLY SURFACE WINDS. CURRENTLY IT APPEARS THAT 20 TO 25 MPH
WINDS WITH GUSTS OF 35 MPH CAN BE EXPECTED SUNDAY AFTERNOON.

KJB

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KILX 010827
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
327 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

&&

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 010827
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
327 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

&&

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 010827
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
327 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

&&

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 010827
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
327 AM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

HIGH PRESSURE REMAINS SITUATED SOUTHWEST OF THE AREA WITH A WEAK
BOUNDARY EXTENDING FROM NORTHERN MO TO SOUTHERN IL. ISOLATES SHOWERS
AND STORMS HAVE DEVELOPED ALONG THIS BOUNDARY IN NORTHERN MO
OVERNIGHT AND ARE MOVING SOUTHEAST. BASED ON RADAR TRENDS BELIEVE
THESE WILL DISSIPATE AS MORNING ARRIVES AND SHOULD REMAIN JUST
SOUTHWEST OF THE CWA DURING THE EARLY MORNING HOURS. SO WILL NOT BE
INCLUDING ANY POPS TO COVER THESE...AT THIS TIME. EXPECTING HIGH
PRESSURE TO CONTINUE TO DOMINATE THE WEATHER ACROSS THE CWA
REMAINDER OF THE DAYTIME HOURS. MODELS SUGGEST A CLUSTER OF STORMS
DEVELOPING THIS AFTERNOON WELL WEST OF THE AREA BUT NOT ARRIVING IN
THE CWA UNTIL LATE TONIGHT...SO NO POPS DURING THE DAY. TEMPS WILL
BE WARM AGAIN TODAY AND LIKE YESTERDAY...EXPECTING UPPER 80S ACROSS
THE AREA.

&&

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT AUG 1 2015

WARMING TREND CONTINUING INTO THE OVERNIGHT WITH TONIGHTS LOWS BEING
A BIT WARMER IN THE UPPER 60S/NEAR 70 AS SOUTHERLY FLOW DOMINATES
AND THE SFC RIDGE SHIFTS SLIGHTLY MORE TO THE EAST.  AN MCS ON TRACK
TO COME INTO THE MIDWEST IN THE OVERNIGHT HOURS BRINGING POPS NW OF
THE IL RIVER VALLEY BEFORE SUNRISE ON SUNDAY.  SUNDAY THE SYSTEM
DRAGS A COLD FRONT INTO THE REGION BUT AGAIN, THE SYSTEM STALLS THE
BOUNDARY INVOF ILX AND SOME DISCREPANCIES IN THE MODELS AS TO WHERE
IT WILL STALL BEFORE THE NEXT WAVE RIPPLES THROUGH.  IN THE SHORTER
TERM, SUNDAYS SYSTEM HAS MORE CONSISTENCY AND THE BETTER CHANCE FOR
PRECIP.  BEYOND SUNDAY, MON NIGHT/TUES IS ANOTHER WAVE MOVING ALONG
THE REMNANT BOUNDARY.  FROM MIDWEEK TO THE END OF THE FORECAST, THE
MODELS DIVERGE CONSIDERABLY, WITH ABOUT A 12 HR DIFFERENCE IN THE
SERIES OF WAVES IN A WEAK NORTHWESTERLY FLOW PATTERN.  AS A RESULT,
THE SUPERBLEND IS SATURATED WITH LOW POPS OFF AND ON AS A WESTERN
MID LEVEL RIDGE TRAPS HIGH TEMPS OVER THE DESERT SW.  COOLING TREND
IS BROADCAST FOR THE MIDWEST THROUGH THE LATTER HALF OF THE WORK
WEEK UNDER INCREASINGLY NWRLY FLOW/AMPLIFYING 500-700MB WAVE
PATTERN.  HOWEVER, THE UPPER LOW REMAINS UP BETWEEN THE GREAT LAKES
AND HUDSON BAY AND RELATIVELY BROAD WITH VERY LITTLE IN THE WAY OF
AGGRESSIVE WAVES DIGGING IT OUT.  NOT CONVINCED OF ANY ONE SOLUTION
AT THIS TIME AND THE WIDE SPREAD CHANCE POPS REMAIN THE BEST OPTION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KLOT 010735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 010735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 010735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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



000
FXUS63 KLOT 010735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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

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




000
FXUS63 KLOT 010559
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 010559
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 010446
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1146 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.

&&

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

$$

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



000
FXUS63 KILX 010446
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1146 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.

&&

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

$$

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



000
FXUS63 KILX 010446
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1146 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.

&&

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

$$

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



000
FXUS63 KILX 010446
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1146 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY STALLED
OUT SOUTH OF THE CENTRAL IL TERMINALS. ISOLATED SHOWERS ALONG THE
BOUNDARY WILL CONTINUE EARLY IN THE OVERNIGHT HOURS...BUT THESE
ARE EXPECTED TO REMAIN SOUTH OF THE CENTRAL IL TERMINALS AND ONLY
EXPECTING SCATTERED SCATTERED CLOUD COVER AT KSPI AND PERHAPS
KDEC. WINDS NW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY. SW WINDS DECREASING AFTER 00Z.

&&

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

$$

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



000
FXUS63 KLOT 010309
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1009 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KLOT 010309
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1009 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 010309
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1009 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 010309
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1009 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

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:
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000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 010158
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 858 PM CDT FRI JUL 31 2015

A FEW ISOLATED THUNDERSTORMS HAVE MANAGED TO FORM ALONG A STALLED
FRONTAL BOUNDARY IN FAR WEST-CENTRAL IL AND COULD REACH INTO
SCHUYLER...CASS...SCOTT...AND MORGAN COUNTIES THIS EVENING. CLOUD
COVER ASSOCIATED WITH STORMS FORMING ALONG THE BOUNDARY TOWARD THE
WEST OVER THE MISSOURI/IOWA BORDER CONTINUE TO SPREAD ACROSS THE
SOUTHERN PORTIONS OF THE CENTRAL IL FORECAST AREA. HAVE UPDATED
FORECASTS FOR THESE TRENDS. OTHERWISE...FORECAST IS ON TRACK FOR A
MOSTLY CLEAR NIGHT ONCE THE CLOUD BAND SLIPS SOUTHWARD...WITH
LOWS REACHING THE LOW TO MID 60S AND LIGHT WEST-NORTHWEST WINDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.


&&

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

$$

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




000
FXUS63 KILX 312341
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
641 PM CDT FRI JUL 31 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.

&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...ONTON




000
FXUS63 KILX 312341
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
641 PM CDT FRI JUL 31 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS AS HIGH
PRESSURE CONTINUES OVER THE AREA WITH A FRONTAL BOUNDARY PUSHED
JUST SOUTH OF THE CENTRAL IL TERMINALS. CONVECTION OVER NW
MISSOURI/SW IOWA THIS EVENING WILL CAUSE SOME MID AND HIGH CLOUD
COVER TO DRIFT EASTWARD OVER THE SOUTHERN TERMINALS KSPI-
KDEC...BUT DRY CONDITIONS AND VFR FLIGHT CATEGORY WILL CONTINUE.
WINDS WNW 3-5 KTS OVERNIGHT...BECOMING SW 8-12 KTS AFTER 15Z
SATURDAY.

&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...ONTON



000
FXUS63 KLOT 312338
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 312338
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 312338
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* SMALL CHANCE FOR SHRA SAT MORNING AND SMALL CHANCE OF TSRA IN
  THE AFTERNOON.


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

GUSTY WEST-NORTHWEST WINDS EARLY THIS EVENING WILL QUICKLY
DIMINISH IN SPEED AROUND SUNDOWN...SIMILAR TO TRENDS THE PAST TWO
DAYS. A SUBTLE DISTURBANCE WILL MOVE SOUTHEASTWARD LATE TONIGHT
AND INTO SATURDAY MORNING ACROSS SOUTHWEST WI AND NORTHERN IL.
THIS COULD INDUCE A FEW SHOWERS AND A STRAY STORM...SIMILAR TO
WHAT HAPPENED EARLY THIS MORNING...ALTHOUGH LIKELY A COUPLE HOURS
LATER IF SO. THE COVERAGE IS VERY LIKELY TO REMAIN ISOLATED IF
DEVELOPMENT CAN OCCUR DUE TO LIMITED DEEP LAYER SATURATION.
CONVERGENCE OF THE WINDS ALONG ANOTHER SUBTLE AND WEAK FRONTAL
BOUNDARY WILL MOVE OVER THE AREA IN THE AFTERNOON AND WITH THIS
CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS DEVELOPING. AGAIN
LOW MOISTURE THROUGH THE ATMOSPHERIC DEPTH SHOULD KEEP COVERAGE
ISOLATED. WINDS ON SATURDAY WILL ONCE AGAIN BE FROM THE WEST WITH
FREQUENT AFTERNOON GUSTS...HOWEVER AT A LOWER MAGNITUDE THAN
RECENT DAYS.


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

* LOW IN ANY PRECIP OVER THE AIRFIELDS SATURDAY AS COVERAGE SHOULD
  BE ISOLATED IF DEVELOPMENT OCCURS.


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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 312201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
501 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST-NORTHWEST WINDS GUSTING TO AROUND 25KT THROUGH 00Z.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ/MTF

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH IN WIND SPEED/DIRECTION.

* LOW IN ANY SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ/MTF

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 312201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
501 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST-NORTHWEST WINDS GUSTING TO AROUND 25KT THROUGH 00Z.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ/MTF

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH IN WIND SPEED/DIRECTION.

* LOW IN ANY SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ/MTF

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 312201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
501 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST-NORTHWEST WINDS GUSTING TO AROUND 25KT THROUGH 00Z.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ/MTF

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH IN WIND SPEED/DIRECTION.

* LOW IN ANY SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ/MTF

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 312201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
501 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST-NORTHWEST WINDS GUSTING TO AROUND 25KT THROUGH 00Z.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ/MTF

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH IN WIND SPEED/DIRECTION.

* LOW IN ANY SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ/MTF

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 312018
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
318 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS WITH GUSTS AROUND 25KT THIS AFTERNOON.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 312018
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
318 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
304 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

MAIN CONCERN FOR THE LATTER PORTION OF THE WEEKEND FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT WILL BE THE CHANCES FOR THUNDERSTORMS
THROUGH THIS PERIOD AS WELL AS TEMPERATURES FOR SUNDAY AFTERNOON.
THE MAIN ADJUSTMENTS TO THE GOING FORECAST WERE TO TREND A LITTLE
SLOWER WITH THE PROGRESSION OF THE NEXT COLD FRONT DROPPING THROUGH
THE AREA FROM NORTHWEST TO SOUTHEAST.

THE LARGER SCALE MODELS ARE TRENDING TO A MORE CONSISTENT SOLUTION
THAT THE SHORTER RANGE GUIDANCE WITH THE PROGRESSION OF THE FRONT
AND THE UPPER LEVEL PATTERN DRIVING THE ASSOCIATED SFC FEATURES.
THE GENERAL TREND THROUGH THE REMAINDER OF THE WEEKEND AND EVEN INTO
EARLY NEXT WEEK WILL BE TO CONTINUE TO AMPLIFY THE UPPER RIDGE OVER
THE WRN CONUS WHILE A DEEP UPPER LOW REMAINS PARKED INVOF HUDSON
BAY...WHILE BROAD UPPER TROUGHING CONTINUES OVER THE ERN CONUS.
THIS WILL KEEP THE UPPER MIDWEST THROUGH THE GREAT LAKES UNDER NWLY
FLOW ALOFT.

THE VARIOUS MODELS SHOW A SERIES OF IMPULSES DROOPING OUT OF CANADA
IN THE FAST NWLY FLOW ALOFT...AND AS USUAL...IT IS THE TYPICAL
TIMING AND INTENSITY DIFFERENCES AMONG THE MODELS IN HOW THEY HANDLE
THESE FAST MOVING SHORTWAVES WILL HAVE A MAJOR IMPACT ON THE
SENSIBLE WEATHER FEATURES.  GIVEN THE RELATIVE CONSISTENCY BETWEEN
THE GFS/ECMWF...HAVE LARGELY BASED THE FORECAST POPS/WX/QPF ON A 50-
50 BLEND OF THESE 2 MODELS.  THE NET EFFECT HERE IS THAT SATURDAY
NIGHT SHOULD BE DRY...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION ON SUNDAY. THE FORECAST GRIDS FOR
SUNDAY ARE A BIT OF A BROADBRUSH FOR CHANCE SHRA/TSRA ACROSS THE
ENTIRE CWA THROUGH THE DAY AND INTO THE EARLY EVENING...LARGELY IN
DEFERENCE TO THE RETURN OF HIGH DEWPOINT AIR TO THE REGION IN THEN
SWLY SFC FLOW AHEAD OF THE COLD FRONT. ALSO...A NRN STREAM SHORTWAVE
DROPPING THE THE FAST NWLY FLOW ALOFT WILL ALSO HELP ORGANIZE SOME
OF THE TS.  THE GFS/ECMWF ARE BOTH VERY CONSISTENT ON TRACKING THE
SHORTWAVE THROUGH THE AREA BTWN 12-18Z SUNDAY WITH THE BEST FORCING
OVER THE SWRN PORTIONS OF THE CWA...THOUGH SOME TSRA/SHRA CANNOT BE
RULED OUT ELSEWHERE.  WITH TEMPERATURES EXPECTED TO REACH THE MIDDLE
TO UPPER 80S ON SUNDAY AND DEWPOINTS IN THE LOWER 70S AWAY FROM THE
URBANIZED AREAS OF THE CHICAGO METRO...THE AFTERNOON HOURS WILL ALSO
BE PRIMED FOR AT LEAST SCT CONVECTIVE ACTIVITY.  CURRENTLY FEEL THAT
THE TIMING OF THE FROPA...DURG THE LATE EVENING HOURS...WILL BE THE
MAIN LIMITING FACTOR IN THE TS CHANCES FOR SUNDAY EVENING AND INTO
THE OVERNIGHT HOURS.  THERE IS SOME HINT OF WEAK SHORTWAVE ENERGY
RIPPLING THROUGH THE NWLY FLOW ALOFT...BUT WITH THE TIMING OF THE
FROPA EXPECTED TO BE AFTER THE TIMING OF MAX HEATING...WILL CONTINUE
TO BROADBRUSH CHANCE POPS THROUGH THE EVENING.  WHILE THERE IS THE
POSSIBILITY OF MORE ORGANIZED CONVECTION ALONG THE COLD
FRONT...TIMING AT THIS POINT IS A LITTLE TOO UNCERTAIN TO TRY AND
PIN DOWN ANY SPECIFIC AREA AND TIME WITH HIGHER POPS.

FOLLOWING THE PASSAGE OF THE COLD FRONT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING...FORECAST CONFIDENCE WILL WANE THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS THE UPPER LEVEL PATTERN DEAMPLIFIES INTO A
MUCH MORE LOW AMPLITUDE PATTERN ALOFT...WITH THE FAST WESTERLIES
ACROSS THE NRN CONUS.  THE MODELS INDICATE A SERIES OF FAST MOVING
SHORTWAVES MOVING THROUGH THE BELT OF STRONGER WESTERLY FLOW
ALOFT...KEEPING PERIODIC CHANCES FOR PCPN ACROSS THE AREA THROUGH
THE PERIOD.  HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND INTO
THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES WILL ALSO HELP TO
SUPPRESS THE GREATER CHANCES FOR PCPN TO THE SOUTH OF THE
CWA...WHILE SETTING UP GENERALLY ELY FLOW AT THE SFC...RANGING FROM
NELY-SELY THROUGH MUCH OF THE WEEK.  THIS PATTERN WILL BE CONDUCIVE
TO A COOLER TEMPERATURE TRENDS...WITH HIGHS RANGING FROM 5-10
DEGREES BELOW NORMAL...IN THE MIDDLE TO UPPER 70S.

KREIN

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS WITH GUSTS AROUND 25KT THIS AFTERNOON.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
315 PM CDT

FOLLOWING THE PASSAGE OF A COLD FRONT...WINDS ACROSS THE WESTERN
GREAT LAKES HAVE INCREASED TO ARND 20 KT WITH OCNL GUSTS TO ARND
25 KT IN A MODEST NWLY GRADIENT BETWEEN DEEP LOW PRESSURE OVER
HUDSON BAY AND A RIDGE OF HIGH PRESSURE EXTENDING FROM THE NRN
PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY. A SMALL CRAFT
ADVISORY WILL REMAIN IN EFFECT FOR THE IL NEARSHORE WATERS INTO
EARLY EVENING WHERE THE WINDS HAVE BEEN STRONGEST AND MOST GUSTY.
AS THE HIGH BUILDS EAST TONIGHT ACROSS THE MIDDLE MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY...THE PRESSURE GRADIENT WILL RELAX
AND WINDS WILL DIMINISH AND BECOME MORE WESTERLY THROUGH THE
EVENING AND OVERNIGHT TONIGHT...ENDING THE SMALL CRAFT ADVISORY
CONDITIONS. AS THE HIGH CONTINUES TO SETTLE INTO THE SERN CONUS
SUNDAY AND A COLD AND ANOTHER COLD FRONT DROPS PUSHES INTO THE NRN
PLAINS. BRISK SWLY WINDS WILL SET UP ACROSS THE LAKE SATURDAY
NIGHT AND SUNDAY...THOUGH THE GRADIENT IS NOT EXPECTED TO BE VERY
STRONG AND WINDS SHOULD ONLY BE ARND 10-20KT. THE NEXT COLD FRONT
SHOULD SWEEP ACROSS THE LAKE SUNDAY EVENING...TURNING WINDS BACK
TO NWLY AGAIN. HIGH PRESSURE BUILDING ACROSS THE NRN PLAINS AND
ACROSS THE UPPER GREAT LAKES EARLY NEXT WEEK SHOULD THEN LEAD TO A
PERIOD OF GENERALLY EASTERLY FLOW OVER LAKE MICHIGAN FOR MUCH OF
NEXT WEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KILX 312017
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
317 PM CDT FRI JUL 31 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1255 PM CDT FRI JUL 31 2015

WEAK COLD FRONT CONTINUES TO SAG SOUTHWARD INTO NORTH-CENTRAL
ILLINOIS EARLY THIS AFTERNOON. CU-FIELD REMAINS LARGELY ABSENT
ALONG THE BOUNDARY THUS FAR...EXCEPT ACROSS NORTHERN INDIANA INTO
NORTHEAST ILLINOIS. THIS CLOUD TREND FITS VERY WELL WITH THE RAPID
REFRESH...WHICH SHOWS WIDELY SCATTERED CONVECTION DEVELOPING
ACROSS THIS AREA OVER THE NEXT COUPLE OF HOURS...WHILE KEEPING THE
REMAINDER OF THE FRONTAL BOUNDARY TOTALLY DRY. AS A RESULT...WILL
ONLY MENTION VCTS AT KCMI BETWEEN 18Z AND 22Z. FEW-SCT DIURNAL
CLOUDS ALONG/AHEAD OF THE FRONT WILL QUICKLY DISSIPATE TOWARD
SUNSET...WITH CLEAR SKIES EXPECTED TONIGHT THROUGH SATURDAY
MORNING. WINDS WILL INITIALLY BE FROM THE NORTHWEST GUSTING TO
BETWEEN 15 AND 18KT THIS AFTERNOON...THEN WILL BECOME WESTERLY AT
LESS THAN 5KT TONIGHT.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...BARNES




000
FXUS63 KILX 312017
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
317 PM CDT FRI JUL 31 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 315 PM CDT FRI JUL 31 2015

19Z/2PM SURFACE ANALYSIS SHOWS WEAK COLD FRONT SETTLING INTO CENTRAL
ILLINOIS...EXTENDING FROM NEAR RANTOUL TO JUST SOUTH OF QUINCY.
MINIMAL CONVERGENCE ALONG THE FRONT AND AN OVERALL LACK OF DEEP
LAYER MOISTURE HAS LARGELY PREVENTED CONVECTION.  THE EXCEPTION HAS
BEEN FURTHER NORTHEAST ACROSS NORTHERN INDIANA WHERE A FEW CLUSTERS
OF THUNDERSTORMS HAVE DEVELOPED.  HRRR CONTINUES TO OVER-EMPHASIZE
DEWPOINT POOLING ALONG THE FRONT AND PRODUCES NUMEROUS THUNDERSTORMS
WITH ITS 1 AND 2-HOUR FORECAST.  MEANWHILE...THE RAPID REFRESH HAS
CONSISTENTLY PRESENTED A MORE REALISTIC SCENARIO...SUGGESTING ONLY
ISOLATED STORMS MAINLY ACROSS THE E/NE KILX CWA OVER THE NEXT 2-4
HOURS.  GIVEN THIS IS THE LOCATION WHERE CU-FIELD IS CURRENTLY MOST
PRONOUNCED...WILL CONTINUE TO FOLLOW THIS SOLUTION CLOSELY.  AS A
RESULT...WILL CARRY SLIGHT CHANCE POPS ALONG/NORTHEAST OF A
CHAMPAIGN TO MARSHALL LINE THROUGH THE AFTERNOON.  ANY ISOLATED
CONVECTION THAT DEVELOPS WILL QUICKLY DISSIPATE TOWARD
SUNSET...FOLLOWED BY MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
SLIGHTLY DRIER AIRMASS WILL TRICKLE IN FROM THE NORTHWEST ONCE THE
FRONT PASSES...WITH OVERNIGHT LOW TEMPERATURES DROPPING INTO THE
LOWER TO MIDDLE 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 315 PM CDT FRI JUL 31 2015

OVERALL A FAIRLY PERSISTENT WNW FLOW PATTERN WILL REMAIN ACROSS IL
AND MUCH OF THE MIDWEST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. QUITE A BIT OF MODEL UNCERTAINTY REGARDING A BREAKDOWN OF THE
WESTERN RIDGE AND DEEPENING OF THE EASTERN TROUGH FOR THE MIDDLE OF
NEXT WEEK.

IN THE NEAR TERM...VERY WARM AND INCREASINGLY HUMID CONDITIONS WILL
BE ON TAP FOR CENTRAL AND EASTERN IL SATURDAY. AN ADVANCING WARM
FRONT AND A CLUSTER OF CONVECTION FROM IOWA/NEBRASKA IS EXPECTED TO
APPROACH AREAS WEST OF THE IL RIVER VALLEY LATE SATURDAY NIGHT AND
INTO SUNDAY MORNING. THE REMNANTS OF THE EARLY MORNING T-STORMS ARE
THEN EXPECTED TO SPREAD ACROSS MOST OF CENTRAL AND EASTERN IL SUNDAY
MORNING AND EARLY AFTERNOON. RESIDUAL BOUNDARIES FROM THIS
CONVECTION SHOULD RESULT IN REDEVELOPMENT OF T-STORMS SUNDAY
AFTERNOON AND INTO THE EVENING...ESPECIALLY ALONG AND NORTH OF I-74.
SOME OF THE STORMS LATER IN THE DAY SUNDAY COULD BE STRONG...MAINLY
DUE TO MODERATE LEVELS OF WIND SHEAR AND INSTABILITY.

MOST OF THE FORECAST AREA WILL BE IN THE WARM SECTOR OF AN ADVANCING
FRONTAL BOUNDARY...YIELDING VERY WARM AND SOMEWHAT HUMID CONDITIONS
MONDAY. THE AFOREMENTIONED FRONT IS EXPECTED TO SLOWLY MOVE INTO
CENTRAL ILLINOIS MONDAY NIGHT AND THEN REMAIN NEARLY STATIONARY FOR
MUCH OF THE WEEK. THIS SHOULD RESULT IN A RATHER UNSETTLED WEATHER
PATTERN WITH THE POTENTIAL FOR SEVERAL PERIODS OF RAIN FROM LATE
MONDAY...ON AND OFF...THROUGH THE END OF THE WEEK.

THE UNCERTAINTY IN THE MODELS REVOLVES AROUND THE DETAILS OF
POSSIBLE SHORTWAVE ENERGY BREAKING THROUGH THE WESTERN U.S. RIDGE
AND INTERACTING WITH THE FRONT. THE GFS IS A BIT MORE AGGRESSIVE WITH
THIS THAN THE EUROPEAN MODEL. HOWEVER...THE EUROPEAN NOT ONLY
UNDERPLAYS THE AFFECTS OF THIS BUT KEEPS THE SURFACE FRONT FARTHER
NORTH. UNTIL THE DETAILS ARE WORKED OUT IT IS HARD TO PIN DOWN
WHERE A THREAT OF PERSISTENT...POSSIBLY HEAVY RAIN MAY SET UP THE
MIDDLE OF NEXT WEEK. THUS...WILL NOT MAKE TOO MANY MAJOR CHANGES
TO THE FORECAST AND KEEP CHANCE POPS FOR THUNDERSTORMS ACROSS A
LARGE PART OF THE FORECAST AREA.

THE ONE THING THE MODELS DO AGREE ON IS THAT WITH THE PERIODS OF
CONVECTION AND RESIDUAL CLOUD COVER...TEMPERATURES SHOULD BE BELOW
SEASONAL NORMALS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1255 PM CDT FRI JUL 31 2015

WEAK COLD FRONT CONTINUES TO SAG SOUTHWARD INTO NORTH-CENTRAL
ILLINOIS EARLY THIS AFTERNOON. CU-FIELD REMAINS LARGELY ABSENT
ALONG THE BOUNDARY THUS FAR...EXCEPT ACROSS NORTHERN INDIANA INTO
NORTHEAST ILLINOIS. THIS CLOUD TREND FITS VERY WELL WITH THE RAPID
REFRESH...WHICH SHOWS WIDELY SCATTERED CONVECTION DEVELOPING
ACROSS THIS AREA OVER THE NEXT COUPLE OF HOURS...WHILE KEEPING THE
REMAINDER OF THE FRONTAL BOUNDARY TOTALLY DRY. AS A RESULT...WILL
ONLY MENTION VCTS AT KCMI BETWEEN 18Z AND 22Z. FEW-SCT DIURNAL
CLOUDS ALONG/AHEAD OF THE FRONT WILL QUICKLY DISSIPATE TOWARD
SUNSET...WITH CLEAR SKIES EXPECTED TONIGHT THROUGH SATURDAY
MORNING. WINDS WILL INITIALLY BE FROM THE NORTHWEST GUSTING TO
BETWEEN 15 AND 18KT THIS AFTERNOON...THEN WILL BECOME WESTERLY AT
LESS THAN 5KT TONIGHT.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...BARNES



000
FXUS63 KLOT 311923
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
223 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS WITH GUSTS AROUND 25KT THIS AFTERNOON.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 311923
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
223 PM CDT FRI JUL 31 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS WITH GUSTS AROUND 25KT THIS AFTERNOON.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1257 PM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WEST/NORTHWEST WINDS WITH GUSTS AROUND 25KT THIS AFTERNOON.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1257 PM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WEST/NORTHWEST WINDS WITH GUSTS AROUND 25KT THIS AFTERNOON.

* ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE SATURDAY MORNING.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

SURFACE TROUGH MOVING THROUGH THE AREA EARLY THIS AFTERNOON WITH
VFR CONDITIONS IN PLACE...AND WITH WEST/NORTHWEST WINDS INCREASING
AT THIS TIME. VFR CONDITIONS WILL REMAIN TODAY INTO TONIGHT WHILE
ANY SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON REMAINS WELL
SOUTH OF THE TERMINALS. THESE STRONGER WESTERLY WINDS WILL LIKELY
PERSIST THROUGH EARLY EVENING...WITH EXPECTED GUSTS AROUND 25KT.
THERE DOES APPEAR TO BE SMALL WINDOW SATURDAY MORNING FOR ISOLATED
PRECIP TO MOVE ACROSS THE TERMINALS. THEY WILL LIKELY BE ONLY
SHOWERS...BUT WITH THUNDER DEFINITELY NOT OUT OF THE QUESTION.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH SHOWERS/THUNDERSTORMS SATURDAY MORNING.

RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KILX 311755
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1255 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 1026 AM CDT FRI JUL 31 2015

15Z/10AM SURFACE ANALYSIS SHOWS WEAK COLD FRONT DROPPING SOUTHWARD
THROUGH WISCONSIN/IOWA. SO FAR VERY LITTLE CU HAS DEVELOPED
ALONG/AHEAD OF THE BOUNDARY...HOWEVER SOME 12Z MODELS ARE STILL
TRYING TO FIRE A FEW THUNDERSTORMS LATE THIS AFTERNOON INTO THE
EVENING. AIRMASS IS NOT PARTICULARLY MOIST AND CONVERGENCE ALONG
THE FRONT IS PALTRY AT BEST...SO AM NOT EXPECTING MUCH PRECIP AT
ALL. WILL MAINTAIN JUST SLIGHT CHANCE POPS AFTER 21Z...WITH
AFTERNOON HIGHS TOPPING OUT IN THE UPPER 80S TO AROUND 90 DEGREES.
CURRENT FORECAST IS RIGHT ON TRACK...SO NO UPDATE IS NEEDED AT
THIS TIME.

&&

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1255 PM CDT FRI JUL 31 2015

WEAK COLD FRONT CONTINUES TO SAG SOUTHWARD INTO NORTH-CENTRAL
ILLINOIS EARLY THIS AFTERNOON. CU-FIELD REMAINS LARGELY ABSENT
ALONG THE BOUNDARY THUS FAR...EXCEPT ACROSS NORTHERN INDIANA INTO
NORTHEAST ILLINOIS. THIS CLOUD TREND FITS VERY WELL WITH THE RAPID
REFRESH...WHICH SHOWS WIDELY SCATTERED CONVECTION DEVELOPING
ACROSS THIS AREA OVER THE NEXT COUPLE OF HOURS...WHILE KEEPING THE
REMAINDER OF THE FRONTAL BOUNDARY TOTALLY DRY. AS A RESULT...WILL
ONLY MENTION VCTS AT KCMI BETWEEN 18Z AND 22Z. FEW-SCT DIURNAL
CLOUDS ALONG/AHEAD OF THE FRONT WILL QUICKLY DISSIPATE TOWARD
SUNSET...WITH CLEAR SKIES EXPECTED TONIGHT THROUGH SATURDAY
MORNING. WINDS WILL INITIALLY BE FROM THE NORTHWEST GUSTING TO
BETWEEN 15 AND 18KT THIS AFTERNOON...THEN WILL BECOME WESTERLY AT
LESS THAN 5KT TONIGHT.

&&

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

$$

UPDATE...BARNES
SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...BARNES



000
FXUS63 KILX 311755
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1255 PM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 1026 AM CDT FRI JUL 31 2015

15Z/10AM SURFACE ANALYSIS SHOWS WEAK COLD FRONT DROPPING SOUTHWARD
THROUGH WISCONSIN/IOWA. SO FAR VERY LITTLE CU HAS DEVELOPED
ALONG/AHEAD OF THE BOUNDARY...HOWEVER SOME 12Z MODELS ARE STILL
TRYING TO FIRE A FEW THUNDERSTORMS LATE THIS AFTERNOON INTO THE
EVENING. AIRMASS IS NOT PARTICULARLY MOIST AND CONVERGENCE ALONG
THE FRONT IS PALTRY AT BEST...SO AM NOT EXPECTING MUCH PRECIP AT
ALL. WILL MAINTAIN JUST SLIGHT CHANCE POPS AFTER 21Z...WITH
AFTERNOON HIGHS TOPPING OUT IN THE UPPER 80S TO AROUND 90 DEGREES.
CURRENT FORECAST IS RIGHT ON TRACK...SO NO UPDATE IS NEEDED AT
THIS TIME.

&&

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1255 PM CDT FRI JUL 31 2015

WEAK COLD FRONT CONTINUES TO SAG SOUTHWARD INTO NORTH-CENTRAL
ILLINOIS EARLY THIS AFTERNOON. CU-FIELD REMAINS LARGELY ABSENT
ALONG THE BOUNDARY THUS FAR...EXCEPT ACROSS NORTHERN INDIANA INTO
NORTHEAST ILLINOIS. THIS CLOUD TREND FITS VERY WELL WITH THE RAPID
REFRESH...WHICH SHOWS WIDELY SCATTERED CONVECTION DEVELOPING
ACROSS THIS AREA OVER THE NEXT COUPLE OF HOURS...WHILE KEEPING THE
REMAINDER OF THE FRONTAL BOUNDARY TOTALLY DRY. AS A RESULT...WILL
ONLY MENTION VCTS AT KCMI BETWEEN 18Z AND 22Z. FEW-SCT DIURNAL
CLOUDS ALONG/AHEAD OF THE FRONT WILL QUICKLY DISSIPATE TOWARD
SUNSET...WITH CLEAR SKIES EXPECTED TONIGHT THROUGH SATURDAY
MORNING. WINDS WILL INITIALLY BE FROM THE NORTHWEST GUSTING TO
BETWEEN 15 AND 18KT THIS AFTERNOON...THEN WILL BECOME WESTERLY AT
LESS THAN 5KT TONIGHT.

&&

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

$$

UPDATE...BARNES
SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...BARNES




000
FXUS63 KLOT 311601
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1101 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS AROUND 14KT WITH GUSTS BETWEEN 21-26KT.
  GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 311601
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1101 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS AROUND 14KT WITH GUSTS BETWEEN 21-26KT.
  GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311601
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1101 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS AROUND 14KT WITH GUSTS BETWEEN 21-26KT.
  GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 311601
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1101 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST/NORTHWEST WINDS AROUND 14KT WITH GUSTS BETWEEN 21-26KT.
  GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KILX 311531
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1031 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 1026 AM CDT FRI JUL 31 2015

15Z/10AM SURFACE ANALYSIS SHOWS WEAK COLD FRONT DROPPING SOUTHWARD
THROUGH WISCONSIN/IOWA. SO FAR VERY LITTLE CU HAS DEVELOPED
ALONG/AHEAD OF THE BOUNDARY...HOWEVER SOME 12Z MODELS ARE STILL
TRYING TO FIRE A FEW THUNDERSTORMS LATE THIS AFTERNOON INTO THE
EVENING. AIRMASS IS NOT PARTICULARLY MOIST AND CONVERGENCE ALONG
THE FRONT IS PALTRY AT BEST...SO AM NOT EXPECTING MUCH PRECIP AT
ALL. WILL MAINTAIN JUST SLIGHT CHANCE POPS AFTER 21Z...WITH
AFTERNOON HIGHS TOPPING OUT IN THE UPPER 80S TO AROUND 90 DEGREES.
CURRENT FORECAST IS RIGHT ON TRACK...SO NO UPDATE IS NEEDED AT
THIS TIME.

&&

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 610 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL AT ALL SITES NEXT 24HRS. A WEAK FRONT
WILL DROP INTO THE AREA TODAY. WITH FORCING WEAK AND VERY LIMITED
MOISTURE...BELIEVE ONLY ISOLATED STORMS ARE POSSIBLE IN THE AREA
LATE THIS AFTERNOON AND INTO EARLY EVENING. WILL KEEP THE VCTS AT
ALL SITES FOR WHEN BEST CHANCE IS. SHOULD BE ONLY FEW TO SCATTERED
CLOUDS THROUGH THE PERIOD AS WELL. WINDS WILL BE WEST TO SOUTHWEST
AHEAD OF THE FRONT AND THEN BECOME NORTHWEST BEHIND THE FRONT.


&&

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

$$

UPDATE...BARNES
SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...AUTEN




000
FXUS63 KILX 311531
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1031 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 1026 AM CDT FRI JUL 31 2015

15Z/10AM SURFACE ANALYSIS SHOWS WEAK COLD FRONT DROPPING SOUTHWARD
THROUGH WISCONSIN/IOWA. SO FAR VERY LITTLE CU HAS DEVELOPED
ALONG/AHEAD OF THE BOUNDARY...HOWEVER SOME 12Z MODELS ARE STILL
TRYING TO FIRE A FEW THUNDERSTORMS LATE THIS AFTERNOON INTO THE
EVENING. AIRMASS IS NOT PARTICULARLY MOIST AND CONVERGENCE ALONG
THE FRONT IS PALTRY AT BEST...SO AM NOT EXPECTING MUCH PRECIP AT
ALL. WILL MAINTAIN JUST SLIGHT CHANCE POPS AFTER 21Z...WITH
AFTERNOON HIGHS TOPPING OUT IN THE UPPER 80S TO AROUND 90 DEGREES.
CURRENT FORECAST IS RIGHT ON TRACK...SO NO UPDATE IS NEEDED AT
THIS TIME.

&&

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 610 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL AT ALL SITES NEXT 24HRS. A WEAK FRONT
WILL DROP INTO THE AREA TODAY. WITH FORCING WEAK AND VERY LIMITED
MOISTURE...BELIEVE ONLY ISOLATED STORMS ARE POSSIBLE IN THE AREA
LATE THIS AFTERNOON AND INTO EARLY EVENING. WILL KEEP THE VCTS AT
ALL SITES FOR WHEN BEST CHANCE IS. SHOULD BE ONLY FEW TO SCATTERED
CLOUDS THROUGH THE PERIOD AS WELL. WINDS WILL BE WEST TO SOUTHWEST
AHEAD OF THE FRONT AND THEN BECOME NORTHWEST BEHIND THE FRONT.


&&

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

$$

UPDATE...BARNES
SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...AUTEN



000
FXUS63 KLOT 311409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 311409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER/RODRIGUEZ

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER/RODRIGUEZ

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 311145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 311145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 311145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS INCREASE BY MID-MORNING TO 12-14KT WITH GUSTS BETWEEN
  20-25KT. GUSTS DIMINISH SHORTLY AFTER SUNSET.

BEACHLER

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

HIGH PRESSURE WILL CONTINUE TO PROVIDE VFR CONDS ACROSS THE
REGION TODAY. MIXING WILL INCREASE BY MID- MORNING...RESULTING IN
GUSTY WEST WINDS DEVELOPING. CURRENT INDICATIONS ARE THAT GUSTS
WILL BE BETWEEN 20-25KT...HOWEVER IT IS POSSIBLE A FEW GUSTS COULD
APPROACH 26-28KT. MIXING WILL QUICKLY DISSIPATE SHORTLY AFTER
SUNSET...WITH WIND SPEEDS FALLING BACK TO ARND 10KT. MINIMAL CLOUD
COVER AGAIN TODAY...WITH EXCEPTION OF A THIN CIRRUS CLOUD DECK.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...MAINLY VFR. CHANCE OF SHOWERS/THUNDERSTORMS LATE.

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
TUESDAY...DRY/VFR. NORTHEAST WINDS.
WEDNESDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN.

BEACHLER

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KILX 311110
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
610 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 610 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL AT ALL SITES NEXT 24HRS. A WEAK FRONT
WILL DROP INTO THE AREA TODAY. WITH FORCING WEAK AND VERY LIMITED
MOISTURE...BELIEVE ONLY ISOLATED STORMS ARE POSSIBLE IN THE AREA
LATE THIS AFTERNOON AND INTO EARLY EVENING. WILL KEEP THE VCTS AT
ALL SITES FOR WHEN BEST CHANCE IS. SHOULD BE ONLY FEW TO SCATTERED
CLOUDS THROUGH THE PERIOD AS WELL. WINDS WILL BE WEST TO SOUTHWEST
AHEAD OF THE FRONT AND THEN BECOME NORTHWEST BEHIND THE FRONT.

&&

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

$$

SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...AUTEN



000
FXUS63 KILX 311110
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
610 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 610 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL AT ALL SITES NEXT 24HRS. A WEAK FRONT
WILL DROP INTO THE AREA TODAY. WITH FORCING WEAK AND VERY LIMITED
MOISTURE...BELIEVE ONLY ISOLATED STORMS ARE POSSIBLE IN THE AREA
LATE THIS AFTERNOON AND INTO EARLY EVENING. WILL KEEP THE VCTS AT
ALL SITES FOR WHEN BEST CHANCE IS. SHOULD BE ONLY FEW TO SCATTERED
CLOUDS THROUGH THE PERIOD AS WELL. WINDS WILL BE WEST TO SOUTHWEST
AHEAD OF THE FRONT AND THEN BECOME NORTHWEST BEHIND THE FRONT.

&&

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

$$

SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...AUTEN



000
FXUS63 KLOT 310908
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
408 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310908
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
408 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 310908
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
408 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310818
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
318 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 310818
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
318 AM CDT FRI JUL 31 2015

.SHORT TERM...
317 AM CDT

THROUGH SATURDAY...

IT SEEMS ODD TO BE TALKING ABOUT UNSEASONABLY DRY CONDITIONS OVER
THE AREA THIS MORNING AFTER THE COUNTLESS HEAVY RAIN EVENTS OVER THE
REGION OVER THE PAST COUPLE OF MONTHS WITH PWATS COMMONLY
APPROACHING 2". INSTEAD...PRECIPITABLE WATER VALUES ON YESTERDAYS
ILX RAOB SOUNDINGS INDICATED A VERY DRY ATMOSPHERIC COLUMN...WITH
VALUES UNDER AN INCH. THE 12 UTC THURSDAY RAOB EVEN HAD VALUES DOWN
AROUND 0.7 INCHES...WHICH IS NEAR THE CLIMATOLOGICAL MINIMUM FOR
THIS TIME OF YEAR. SO...THE ATMOSPHERIC COLUMN DOES NOT GET MUCH
DRIER THIS TIME OF YEAR. WITH SIMILAR PRECIPITABLE WATER VALUES
EXPECTED ACROSS MUCH OF THE AREA TODAY...IT APPEARS THE THREAT FOR
SHOWERS AND STORMS WILL BE VERY LOW.

A WEAK SURFACE BOUNDARY WILL SHIFT OVER THE AREA TODAY. HOWEVER...NO
BIG AIRMASS CHANGES ARE EXPECTED IN ITS WAKE. THEREFORE...IT APPEARS
THAT IT WILL BE ANOTHER VERY WARM...BUT UNSEASONABLY DRY AND BREEZY
DAY ACROSS THE REGION. DEW POINTS ACROSS THE AREA THIS MORNING
REMAIN IN THE UPPER 50S ACROSS MUCH OF NORTHERN ILLINOIS...WITH
LOWER TO MID 60S GENERALLY SOUTH OF INTERSTATE 80. THESE DRY DEW
POINTS WILL LIKELY DROP SEVERAL DEGREES AGAIN TODAY...ESPECIALLY
OVER NORTHEASTERN ILLINOIS AS MIXING TO...OR JUST ABOVE...800 MB IN
THIS EXTREMELY DRY AIRMASS...LIKELY RESULTING IN UPPER 40 TO LOWER
50 DEWPOINTS AT THE SURFACE OVER NORTHEASTERN ILLINOIS. GIVEN THAT
TEMPERATURES WILL LIKELY WARM WELL INTO THE 80S AGAIN TODAY...AS
THEY DID YESTERDAY...THIS WOULD SUGGEST THAT THE RELATIVE HUMIDITY
VALUES WILL DROP AS LOW AS 25% IN SOME PLACES ACROSS NORTHEASTERN
ILLINOIS. THESE DRY CONDITIONS IN COMBINATION WITH AFTERNOON WINDS
GUSTING UP TO NEAR 25 KT COULD RESULT IN NEAR RED FLAG CRITERIA
CONDITIONS BELIEVE IT OR NOT. HOWEVER...IT APPEARS THIS AREA WILL BE
CONFINED TO THE MORE URBAN AREAS IN AND AREA CHICAGO...WHERE THE
DRIEST CONDITIONS WILL DEVELOP.

WITH THESE DRY CONDITIONS...IT APPEARS THE THREAT FOR SHOWERS AND
STORMS WILL BE VERY LOW OVER NORTHERN ILLINOIS. SOME SLIGHTLY BETTER
LOW LEVEL MOISTURE SOUTH OF INTERSTATE 80 COULD SUPPORT SLIGHTLY
BETTER CHANCES FOR SHOWER/STORM DEVELOPMENT THIS AFTERNOON.
HOWEVER...I HAVE OPTED TO LEAVE THE MENTION OUT OF THE FORECAST. IF
ANY STORMS WERE ABLE TO DEVELOP ACROSS MY SOUTH THIS
AFTERNOON...THEY WOULD LIKELY REMAIN ISOLATED.

SATURDAY LOOKS TO BE ANOTHER WARM AND FAIRLY DRY DAY ACROSS THE
REGION. IT APPEARS OUR NEXT CHANCE OF STORMS WILL HOLD OFF UNTIL
LATER SATURDAY NIGHT. SEE LONG TERM DISCUSSION BELOW FOR MORE ON
THIS.

KJB

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
251 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE EASTERN GREAT
LAKES SAT...WHILE RIDGING PERSIST ACROSS THE WESTERN CONUS. OPER
SOLUTIONS CONTINUE TO FEATURE A MID-LVL WAVE DEVELOPING SAT AFTN
ACROSS THE PLAINS...AND QUICKLY LIFTING EAST AND REACHING THE
FORECAST AREA LATE SAT NGT. INSTABILITY WILL BE ON THE INCREASE AS
THE WAVE SLIDES OVERHEAD...HOWEVER TIMING IS LESS FAVORABLE FOR
WELL ORGANIZED/DEVELOPED THUNDERSTORMS. SOME OF THE GUIDANCE
MEMBERS SUGGEST ARRIVAL OF THE WAVE WILL BE AFTER 6Z SUN.

THE 500MB TROUGH AXIS CONTINUES TO SEND A FEW WEAK LOBES OF
VORTICITY SOUTH ACROSS THE UPPER MIDWEST SUN/MON. MARGINAL
INSTABILITY WILL LINGER SUN/MON...SO WILL MAINTAIN THE MENTION OF
SHOWERS/THUNDERSTORMS. ALTHOUGH AT THIS TIME EXPECT THE BEST CHANCE
FOR THUNDERSTORMS WOULD OCCUR IN MORE OF A DIURNAL COMPONENT...IN
THE AFTERNOON/EVENING TIMEFRAME BOTH DAYS.

ENSEMBLES THEN TREND BACK TOWARDS THE WESTERN RIDGE
DEVELOPING...HELPING TO BRING A SLIGHTLY STRONGER TROUGH BACK ACROSS
THE GREAT LAKES REGION TOWARDS MID-WEEK. MINIMAL SPREAD CONTINUES TO
BE ADVERTISED AMONGST MOST ENSEMBLE MEMBERS...SUGGESTING A
RELATIVELY HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL PUSH ACROSS THE
REGION TUE...WITH UNSEASONABLY COOLER AIR STEADILY ADVECTING SOUTH
WITH A THERMAL TROUGH SETTING UP OVER THE GREAT LAKES REGION. THIS
WILL TRANSITION TEMPS FROM THE MID/UPR 80S SUN/MON...TO AROUND 80
TUE...AND THEN MID/UPR 70S FOR THE REMAINDER OF THE EXTENDED
PERIODS. CHANCES FOR SHOWERS AND ISOLATED THUNDER LOOKS MINIMAL
BEYOND TUE...AND COULD END UP REMAINING DRY AS SOME GUIDANCE
SUGGESTS WEAK ANTI-CYCLONIC FLOW LINGERING OVERHEAD.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
255 AM CDT

THE GRADIENT TIGHTENS UP AGAIN TODAY...WITH WEST/NORTHWEST WINDS
CREATING SOME GUSTY CONDS MAINLY FOR THE SOUTHERN HALF. THIS WILL
CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT THROUGH THIS
AFTERNOON WITH 20-25KT GUSTS...THEN AFTER SUNSET THE GRADIENT
DIMINISHES ALLOWING WINDS TO BECOME LESS GUSTY. WITH HIGH PRESSURE
DRIFTING EAST ACROSS THE OHIO VALLEY SATURDAY...WINDS WILL BE
SLOWLY TURNING SOUTHWESTERLY. THE GRADIENT TIGHTENS LATE IN THE
WEEKEND AS ANOTHER AREA OF LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE WEST. WINDS MAY BECOME GUSTY SUN AFTERNOON. A STRONGER
LOW AND FRONTAL BOUNDARY WILL ARRIVE MONDAY NGT INTO
TUESDAY...WITH WINDS TURNING NORTHWEST TO NORTH.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KILX 310744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
244 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNSET TO NEAR 5 KTS.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...ONTON



000
FXUS63 KILX 310744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
244 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNSET TO NEAR 5 KTS.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...ONTON



000
FXUS63 KILX 310744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
244 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNSET TO NEAR 5 KTS.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...ONTON



000
FXUS63 KILX 310744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
244 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

HIGH PRESSURE RIDGE OVER CENTRAL MO WILL SLIDE SOUTH THIS MORNING
AND ALLOW A WEAK COLD FRONT TO DROP INTO THE AREA FOR THIS
AFTERNOON. CONVERGENCE AND MOISTURE ALONG THIS FRONT WILL BE VERY
LIMITED SO BELIEVE ANY CONVECTION COVERAGE WILL BE VERY SPOTTY. IN
KEEPING WITH THE CURRENT THINKING/FORECAST WITH THIS FRONT...WILL
HAVE A SLIGHT CHANCE OF PCPN IN THE FORECAST FOR LATE THIS
AFTERNOON...IN LINE WITH PEAK HEATING. FORECAST CAPE VALUES REACH
NEAR 1500 WITH VERY LOW SHEAR. SO ONLY EXPECTING ISOLATED
CONVECTION. AFTERNOON TEMPS WILL AGAIN GET QUITE WARM...IN THE
UPPER 80S...WHICH IS AROUND GUIDANCE.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 243 AM CDT FRI JUL 31 2015

NOT A LOT OF CHANGE IN THE UPPER PATTERN EXPECTED THE NEXT FEW
DAYS...AS THE RIDGE CONTINUES TO BUILD ACROSS THE WESTERN U.S. AND A
NORTHWEST FLOW PREVAILING FOR US. LONGER RANGE MODELS EXHIBITING
SOME DIFFERENCES TOWARD THE MIDDLE OF NEXT WEEK AS THE RIDGE STARTS
TO BREAK DOWN AND SHIFT EAST...WITH THE GFS HANGING ON TO THE RIDGE
LONGER...BUT THE NET RESULT WILL BE A GRADUAL COOLING TREND OVER
CENTRAL ILLINOIS BEGINNING ON TUESDAY...WITH HIGHS IN THE 70S IN
MANY AREAS BY THE SECOND HALF OF NEXT WEEK.

PRECIPITATION ISSUES WILL BE TIED TO THE TIMING OF VARIOUS WAVES IN
THE NORTHWEST FLOW...WITH CONFIDENCE LOWERING THROUGH NEXT WEEK AS
THE MODELS DIVERGE. GENERAL AGREEMENT EXISTS ON THE SHORTWAVE
PASSING THROUGH LATE SATURDAY NIGHT...WITH MOST MODELS FEATURING
SOME SORT OF MCS ACTIVITY DEVELOPING TO OUR NORTHWEST AND ROLLING
TOWARD OUR AREA OVERNIGHT. WILL CONTINUE TO FOCUS POP`S ON THE
NORTHWEST HALF OF THE FORECAST AREA LATE SATURDAY NIGHT...AND AREA-
WIDE ON SUNDAY AS THE MCS WEAKENS OVER OUR AREA. STRENGTH OF A
SECOND WAVE SUNDAY NIGHT IS MUCH WEAKER...AND ONLY THE GFS REALLY
GENERATES ANYTHING IN OUR AREA...SO WILL MAINLY GO WITH SLIGHT
CHANCES THEN.

TUESDAY AND WEDNESDAY BECOME MORE OF A QUESTION MARK DUE TO THE
SPEED OF THE BREAKDOWN OF THE RIDGE. SOME INDICATIONS IN THE LONGER
RANGE MODELS OF THE BOUNDARY HANGING UP FOR A TIME MONDAY NIGHT
THROUGH TUESDAY IN A CORRIDOR NORTHWEST-SOUTHEAST OVER CENTRAL
ILLINOIS. THE ECMWF IS THEN MUCH MORE PRONOUNCED WITH A LARGER UPPER
TROUGH MID WEEK GENERATING MORE WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY...WHILE THE GFS MAINLY KEEPS US ON THE COOLER SIDE OF THE
BOUNDARY WITH LIGHT SHOWERS. HAVE LEANED MORE TOWARD THE ECMWF
COVERAGE BUT NOT AS HIGH WITH THE POP`S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNSET TO NEAR 5 KTS.


&&

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

$$

SHORT TERM...AUTEN
LONG TERM...GEELHART
AVIATION...ONTON



000
FXUS63 KLOT 310606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 310606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 310606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 310606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KLOT 310606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT FRI JUL 31 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST WINDS MAINLY 7-10KT OVERNIGHT...INCREASING MID-MORNING WITH
  GUSTS BETWEEN 20-24KT.

BEACHLER

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

HIGH PRESSURE REMAINS OVERHEAD...ALLOWING VFR CONDS TO PREVAIL
THROUGH ENTIRE TAF PERIOD. WINDS WILL REMAIN WESTERLY WITH BETTER
MIXING MID/LATE MORNING INCREASING WINDS TO 12-15KT AND GUSTS
20-24KT. GUSTS DIMINISH AFTER SUNSET...BUT REMAIN WEST. ONLY A FEW
CLOUDS MIDDAY WITH BASES ARND 7-8KFT AGL. OTHERWISE A THIN CIRRUS
SHIELD OVERHEAD.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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



000
FXUS63 KILX 310506
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1206 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 850 PM CDT THU JUL 30 2015

QUIET WEATHER CONDITIONS WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
BRINGS MOSTLY CLEAR SKIES. LIGHT WESTERLY WINDS WILL CONTINUE AT
MOST LOCATIONS AND LOWS WILL DROP TO AROUND THE MID 60S. NO FOG
EXPECTED AS MOISTURE DEPTH REMAINS SHALLOW AND LIGHT WINDS SHOULD
PROMOTE VERTICAL MIXING. NO SIGNIFICANT UPDATES NEEDED THIS
EVENING AS FORECASTS REMAIN ON TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 322 PM CDT THU JUL 30 2015

ASIDE FROM A FEW HIGH/THIN CLOUDS DRIFTING ACROSS MAINLY THE
SOUTHERN KILX CWA THIS AFTERNOON AND EVENING...SKIES WILL BE CLEAR
ACROSS CENTRAL ILLINOIS THROUGH TONIGHT.  WINDS WILL BECOME WESTERLY
AND DIMINISH TO 5 MPH OR LESS AFTER SUNSET...WHILE OVERNIGHT LOW
TEMPERATURES DROP INTO THE LOWER TO MIDDLE 60S.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 322 PM CDT THU JUL 30 2015

BROAD UPPER LEVEL RIDGING IN THE WESTERN HALF OF THE COUNTRY AND
BROAD UPPER LEVEL TROUGHING IN THE EAST WILL EVOLVE INTO HIGHER
AMPLITUDE FLOW BY LATE IN THE WEEKEND. THIS COULD RESULT IN A RETURN
TO A WETTER PATTERN FOR CENTRAL AND EASTERN IL NEXT WEEK. HOWEVER...
DUE TO SOME MODEL UNCERTAINTY WITH THE SPECIFICS OF THIS TRANSITION
THE UNCERTAINTY LEVEL IS HIGH.

IN THE SHORTER TERM...SHORTWAVE TROUGHING IS EXPECTED TO ROTATE INTO
THE GREAT LAKES REGION FROM THE NW...ALLOWING A WEAK FRONT TO MOVE
TOWARD CENTRAL IL BY LATE TOMORROW AFTERNOON. THIS BOUNDARY WILL
PROVIDE THE FOCUS FOR A FEW THUNDERSTORMS. HOWEVER...WEAK
INSTABILITY/LOW LEVEL MOISTURE LEVELS WILL RESULT IN FAIRLY
ISOLATED COVERAGE FROM LATE AFTERNOON INTO THE EVENING HOURS. WILL
STICK WITH SLIGHT CHANCE POPS FOR THIS POTENTIAL. OTHERWISE...A
WEST WIND AND GENERALLY AMPLE SUNSHINE SHOULD GIVE US HIGHS IN THE
UPPER 80S FRI.

SOMEWHAT DRIER AIR WILL FILTER INTO OUR REGION SATURDAY RESULTING IN
PLENTY OF SUN AND TEMPERATURES IN THE MID TO UPPER 80S. AN
INCREASING LOW LEVEL WIND FIELD SATURDAY NIGHT SHOULD RESULT IN AT
LEAST SCATTERED ELEVATED CONVECTION IN THE ILLINOIS RIVER VALLEY AND
POSSIBLY AS FAR EAST AS BMI. BETTER CHANCES FOR RAIN ACROSS
CENTRAL AND EASTERN IL LOOK TO BE SUNDAY AS MCS REMNANTS FROM OUR
WEST MOVE INTO THE AREA. THE PRESENCE OF SCATTERED THUNDERSTORMS
AND ASSOCIATED CLOUDS SHOULD KEEP TEMPERATURES DOWN IN THE LOWER
TO MID 80S FOR SUNDAY.

FORECAST UNCERTAINTY STARTS TO PLAY A ROLE FROM LATER MONDAY THROUGH
MIDWEEK AS MODEL INCONSISTENCIES AND DIFFERENCES APPEAR. THE GFS IS
MUCH FARTHER EAST WITH THE UPPER TROUGH AXIS THAN THE EUROPEAN
MODEL. THEY BOTH SHOW A FRONT SLOWLY APPROACHING AND EVENTUALLY
MOVING THROUGH ILLINOIS. HOWEVER THE GFS IS QUICKER AND THE EUROPEAN
MUCH SLOWER BECAUSE OF THEIR RELATIVE POSITIONS OF THE EASTERN UPPER
TROUGH AXIS. THIS BOUNDARY WOULD SERVE AS THE FOCUS FOR PERIODS OF
SHOWERS AND T-STORMS MUCH OF NEXT WEEK. WILL LEAN TOWARD A BLEND OF
THESE TWO MODELS FOR THE FORECAST NEXT WEEK. HOWEVER...CONFIDENCE IS
LOW AS THE PATTERN EVOLVES AND THE MODELS DEAL WITH CONSISTENCY
ISSUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNET TO NEAR 5 KTS.

&&

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

&&

$$

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




000
FXUS63 KILX 310506
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1206 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 850 PM CDT THU JUL 30 2015

QUIET WEATHER CONDITIONS WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
BRINGS MOSTLY CLEAR SKIES. LIGHT WESTERLY WINDS WILL CONTINUE AT
MOST LOCATIONS AND LOWS WILL DROP TO AROUND THE MID 60S. NO FOG
EXPECTED AS MOISTURE DEPTH REMAINS SHALLOW AND LIGHT WINDS SHOULD
PROMOTE VERTICAL MIXING. NO SIGNIFICANT UPDATES NEEDED THIS
EVENING AS FORECASTS REMAIN ON TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 322 PM CDT THU JUL 30 2015

ASIDE FROM A FEW HIGH/THIN CLOUDS DRIFTING ACROSS MAINLY THE
SOUTHERN KILX CWA THIS AFTERNOON AND EVENING...SKIES WILL BE CLEAR
ACROSS CENTRAL ILLINOIS THROUGH TONIGHT.  WINDS WILL BECOME WESTERLY
AND DIMINISH TO 5 MPH OR LESS AFTER SUNSET...WHILE OVERNIGHT LOW
TEMPERATURES DROP INTO THE LOWER TO MIDDLE 60S.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 322 PM CDT THU JUL 30 2015

BROAD UPPER LEVEL RIDGING IN THE WESTERN HALF OF THE COUNTRY AND
BROAD UPPER LEVEL TROUGHING IN THE EAST WILL EVOLVE INTO HIGHER
AMPLITUDE FLOW BY LATE IN THE WEEKEND. THIS COULD RESULT IN A RETURN
TO A WETTER PATTERN FOR CENTRAL AND EASTERN IL NEXT WEEK. HOWEVER...
DUE TO SOME MODEL UNCERTAINTY WITH THE SPECIFICS OF THIS TRANSITION
THE UNCERTAINTY LEVEL IS HIGH.

IN THE SHORTER TERM...SHORTWAVE TROUGHING IS EXPECTED TO ROTATE INTO
THE GREAT LAKES REGION FROM THE NW...ALLOWING A WEAK FRONT TO MOVE
TOWARD CENTRAL IL BY LATE TOMORROW AFTERNOON. THIS BOUNDARY WILL
PROVIDE THE FOCUS FOR A FEW THUNDERSTORMS. HOWEVER...WEAK
INSTABILITY/LOW LEVEL MOISTURE LEVELS WILL RESULT IN FAIRLY
ISOLATED COVERAGE FROM LATE AFTERNOON INTO THE EVENING HOURS. WILL
STICK WITH SLIGHT CHANCE POPS FOR THIS POTENTIAL. OTHERWISE...A
WEST WIND AND GENERALLY AMPLE SUNSHINE SHOULD GIVE US HIGHS IN THE
UPPER 80S FRI.

SOMEWHAT DRIER AIR WILL FILTER INTO OUR REGION SATURDAY RESULTING IN
PLENTY OF SUN AND TEMPERATURES IN THE MID TO UPPER 80S. AN
INCREASING LOW LEVEL WIND FIELD SATURDAY NIGHT SHOULD RESULT IN AT
LEAST SCATTERED ELEVATED CONVECTION IN THE ILLINOIS RIVER VALLEY AND
POSSIBLY AS FAR EAST AS BMI. BETTER CHANCES FOR RAIN ACROSS
CENTRAL AND EASTERN IL LOOK TO BE SUNDAY AS MCS REMNANTS FROM OUR
WEST MOVE INTO THE AREA. THE PRESENCE OF SCATTERED THUNDERSTORMS
AND ASSOCIATED CLOUDS SHOULD KEEP TEMPERATURES DOWN IN THE LOWER
TO MID 80S FOR SUNDAY.

FORECAST UNCERTAINTY STARTS TO PLAY A ROLE FROM LATER MONDAY THROUGH
MIDWEEK AS MODEL INCONSISTENCIES AND DIFFERENCES APPEAR. THE GFS IS
MUCH FARTHER EAST WITH THE UPPER TROUGH AXIS THAN THE EUROPEAN
MODEL. THEY BOTH SHOW A FRONT SLOWLY APPROACHING AND EVENTUALLY
MOVING THROUGH ILLINOIS. HOWEVER THE GFS IS QUICKER AND THE EUROPEAN
MUCH SLOWER BECAUSE OF THEIR RELATIVE POSITIONS OF THE EASTERN UPPER
TROUGH AXIS. THIS BOUNDARY WOULD SERVE AS THE FOCUS FOR PERIODS OF
SHOWERS AND T-STORMS MUCH OF NEXT WEEK. WILL LEAN TOWARD A BLEND OF
THESE TWO MODELS FOR THE FORECAST NEXT WEEK. HOWEVER...CONFIDENCE IS
LOW AS THE PATTERN EVOLVES AND THE MODELS DEAL WITH CONSISTENCY
ISSUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNET TO NEAR 5 KTS.

&&

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

&&

$$

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



000
FXUS63 KILX 310506
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1206 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 850 PM CDT THU JUL 30 2015

QUIET WEATHER CONDITIONS WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
BRINGS MOSTLY CLEAR SKIES. LIGHT WESTERLY WINDS WILL CONTINUE AT
MOST LOCATIONS AND LOWS WILL DROP TO AROUND THE MID 60S. NO FOG
EXPECTED AS MOISTURE DEPTH REMAINS SHALLOW AND LIGHT WINDS SHOULD
PROMOTE VERTICAL MIXING. NO SIGNIFICANT UPDATES NEEDED THIS
EVENING AS FORECASTS REMAIN ON TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 322 PM CDT THU JUL 30 2015

ASIDE FROM A FEW HIGH/THIN CLOUDS DRIFTING ACROSS MAINLY THE
SOUTHERN KILX CWA THIS AFTERNOON AND EVENING...SKIES WILL BE CLEAR
ACROSS CENTRAL ILLINOIS THROUGH TONIGHT.  WINDS WILL BECOME WESTERLY
AND DIMINISH TO 5 MPH OR LESS AFTER SUNSET...WHILE OVERNIGHT LOW
TEMPERATURES DROP INTO THE LOWER TO MIDDLE 60S.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 322 PM CDT THU JUL 30 2015

BROAD UPPER LEVEL RIDGING IN THE WESTERN HALF OF THE COUNTRY AND
BROAD UPPER LEVEL TROUGHING IN THE EAST WILL EVOLVE INTO HIGHER
AMPLITUDE FLOW BY LATE IN THE WEEKEND. THIS COULD RESULT IN A RETURN
TO A WETTER PATTERN FOR CENTRAL AND EASTERN IL NEXT WEEK. HOWEVER...
DUE TO SOME MODEL UNCERTAINTY WITH THE SPECIFICS OF THIS TRANSITION
THE UNCERTAINTY LEVEL IS HIGH.

IN THE SHORTER TERM...SHORTWAVE TROUGHING IS EXPECTED TO ROTATE INTO
THE GREAT LAKES REGION FROM THE NW...ALLOWING A WEAK FRONT TO MOVE
TOWARD CENTRAL IL BY LATE TOMORROW AFTERNOON. THIS BOUNDARY WILL
PROVIDE THE FOCUS FOR A FEW THUNDERSTORMS. HOWEVER...WEAK
INSTABILITY/LOW LEVEL MOISTURE LEVELS WILL RESULT IN FAIRLY
ISOLATED COVERAGE FROM LATE AFTERNOON INTO THE EVENING HOURS. WILL
STICK WITH SLIGHT CHANCE POPS FOR THIS POTENTIAL. OTHERWISE...A
WEST WIND AND GENERALLY AMPLE SUNSHINE SHOULD GIVE US HIGHS IN THE
UPPER 80S FRI.

SOMEWHAT DRIER AIR WILL FILTER INTO OUR REGION SATURDAY RESULTING IN
PLENTY OF SUN AND TEMPERATURES IN THE MID TO UPPER 80S. AN
INCREASING LOW LEVEL WIND FIELD SATURDAY NIGHT SHOULD RESULT IN AT
LEAST SCATTERED ELEVATED CONVECTION IN THE ILLINOIS RIVER VALLEY AND
POSSIBLY AS FAR EAST AS BMI. BETTER CHANCES FOR RAIN ACROSS
CENTRAL AND EASTERN IL LOOK TO BE SUNDAY AS MCS REMNANTS FROM OUR
WEST MOVE INTO THE AREA. THE PRESENCE OF SCATTERED THUNDERSTORMS
AND ASSOCIATED CLOUDS SHOULD KEEP TEMPERATURES DOWN IN THE LOWER
TO MID 80S FOR SUNDAY.

FORECAST UNCERTAINTY STARTS TO PLAY A ROLE FROM LATER MONDAY THROUGH
MIDWEEK AS MODEL INCONSISTENCIES AND DIFFERENCES APPEAR. THE GFS IS
MUCH FARTHER EAST WITH THE UPPER TROUGH AXIS THAN THE EUROPEAN
MODEL. THEY BOTH SHOW A FRONT SLOWLY APPROACHING AND EVENTUALLY
MOVING THROUGH ILLINOIS. HOWEVER THE GFS IS QUICKER AND THE EUROPEAN
MUCH SLOWER BECAUSE OF THEIR RELATIVE POSITIONS OF THE EASTERN UPPER
TROUGH AXIS. THIS BOUNDARY WOULD SERVE AS THE FOCUS FOR PERIODS OF
SHOWERS AND T-STORMS MUCH OF NEXT WEEK. WILL LEAN TOWARD A BLEND OF
THESE TWO MODELS FOR THE FORECAST NEXT WEEK. HOWEVER...CONFIDENCE IS
LOW AS THE PATTERN EVOLVES AND THE MODELS DEAL WITH CONSISTENCY
ISSUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNET TO NEAR 5 KTS.

&&

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

&&

$$

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



000
FXUS63 KILX 310506
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1206 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 850 PM CDT THU JUL 30 2015

QUIET WEATHER CONDITIONS WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
BRINGS MOSTLY CLEAR SKIES. LIGHT WESTERLY WINDS WILL CONTINUE AT
MOST LOCATIONS AND LOWS WILL DROP TO AROUND THE MID 60S. NO FOG
EXPECTED AS MOISTURE DEPTH REMAINS SHALLOW AND LIGHT WINDS SHOULD
PROMOTE VERTICAL MIXING. NO SIGNIFICANT UPDATES NEEDED THIS
EVENING AS FORECASTS REMAIN ON TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 322 PM CDT THU JUL 30 2015

ASIDE FROM A FEW HIGH/THIN CLOUDS DRIFTING ACROSS MAINLY THE
SOUTHERN KILX CWA THIS AFTERNOON AND EVENING...SKIES WILL BE CLEAR
ACROSS CENTRAL ILLINOIS THROUGH TONIGHT.  WINDS WILL BECOME WESTERLY
AND DIMINISH TO 5 MPH OR LESS AFTER SUNSET...WHILE OVERNIGHT LOW
TEMPERATURES DROP INTO THE LOWER TO MIDDLE 60S.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 322 PM CDT THU JUL 30 2015

BROAD UPPER LEVEL RIDGING IN THE WESTERN HALF OF THE COUNTRY AND
BROAD UPPER LEVEL TROUGHING IN THE EAST WILL EVOLVE INTO HIGHER
AMPLITUDE FLOW BY LATE IN THE WEEKEND. THIS COULD RESULT IN A RETURN
TO A WETTER PATTERN FOR CENTRAL AND EASTERN IL NEXT WEEK. HOWEVER...
DUE TO SOME MODEL UNCERTAINTY WITH THE SPECIFICS OF THIS TRANSITION
THE UNCERTAINTY LEVEL IS HIGH.

IN THE SHORTER TERM...SHORTWAVE TROUGHING IS EXPECTED TO ROTATE INTO
THE GREAT LAKES REGION FROM THE NW...ALLOWING A WEAK FRONT TO MOVE
TOWARD CENTRAL IL BY LATE TOMORROW AFTERNOON. THIS BOUNDARY WILL
PROVIDE THE FOCUS FOR A FEW THUNDERSTORMS. HOWEVER...WEAK
INSTABILITY/LOW LEVEL MOISTURE LEVELS WILL RESULT IN FAIRLY
ISOLATED COVERAGE FROM LATE AFTERNOON INTO THE EVENING HOURS. WILL
STICK WITH SLIGHT CHANCE POPS FOR THIS POTENTIAL. OTHERWISE...A
WEST WIND AND GENERALLY AMPLE SUNSHINE SHOULD GIVE US HIGHS IN THE
UPPER 80S FRI.

SOMEWHAT DRIER AIR WILL FILTER INTO OUR REGION SATURDAY RESULTING IN
PLENTY OF SUN AND TEMPERATURES IN THE MID TO UPPER 80S. AN
INCREASING LOW LEVEL WIND FIELD SATURDAY NIGHT SHOULD RESULT IN AT
LEAST SCATTERED ELEVATED CONVECTION IN THE ILLINOIS RIVER VALLEY AND
POSSIBLY AS FAR EAST AS BMI. BETTER CHANCES FOR RAIN ACROSS
CENTRAL AND EASTERN IL LOOK TO BE SUNDAY AS MCS REMNANTS FROM OUR
WEST MOVE INTO THE AREA. THE PRESENCE OF SCATTERED THUNDERSTORMS
AND ASSOCIATED CLOUDS SHOULD KEEP TEMPERATURES DOWN IN THE LOWER
TO MID 80S FOR SUNDAY.

FORECAST UNCERTAINTY STARTS TO PLAY A ROLE FROM LATER MONDAY THROUGH
MIDWEEK AS MODEL INCONSISTENCIES AND DIFFERENCES APPEAR. THE GFS IS
MUCH FARTHER EAST WITH THE UPPER TROUGH AXIS THAN THE EUROPEAN
MODEL. THEY BOTH SHOW A FRONT SLOWLY APPROACHING AND EVENTUALLY
MOVING THROUGH ILLINOIS. HOWEVER THE GFS IS QUICKER AND THE EUROPEAN
MUCH SLOWER BECAUSE OF THEIR RELATIVE POSITIONS OF THE EASTERN UPPER
TROUGH AXIS. THIS BOUNDARY WOULD SERVE AS THE FOCUS FOR PERIODS OF
SHOWERS AND T-STORMS MUCH OF NEXT WEEK. WILL LEAN TOWARD A BLEND OF
THESE TWO MODELS FOR THE FORECAST NEXT WEEK. HOWEVER...CONFIDENCE IS
LOW AS THE PATTERN EVOLVES AND THE MODELS DEAL WITH CONSISTENCY
ISSUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNET TO NEAR 5 KTS.

&&

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

&&

$$

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



000
FXUS63 KILX 310506
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1206 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 850 PM CDT THU JUL 30 2015

QUIET WEATHER CONDITIONS WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
BRINGS MOSTLY CLEAR SKIES. LIGHT WESTERLY WINDS WILL CONTINUE AT
MOST LOCATIONS AND LOWS WILL DROP TO AROUND THE MID 60S. NO FOG
EXPECTED AS MOISTURE DEPTH REMAINS SHALLOW AND LIGHT WINDS SHOULD
PROMOTE VERTICAL MIXING. NO SIGNIFICANT UPDATES NEEDED THIS
EVENING AS FORECASTS REMAIN ON TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 322 PM CDT THU JUL 30 2015

ASIDE FROM A FEW HIGH/THIN CLOUDS DRIFTING ACROSS MAINLY THE
SOUTHERN KILX CWA THIS AFTERNOON AND EVENING...SKIES WILL BE CLEAR
ACROSS CENTRAL ILLINOIS THROUGH TONIGHT.  WINDS WILL BECOME WESTERLY
AND DIMINISH TO 5 MPH OR LESS AFTER SUNSET...WHILE OVERNIGHT LOW
TEMPERATURES DROP INTO THE LOWER TO MIDDLE 60S.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 322 PM CDT THU JUL 30 2015

BROAD UPPER LEVEL RIDGING IN THE WESTERN HALF OF THE COUNTRY AND
BROAD UPPER LEVEL TROUGHING IN THE EAST WILL EVOLVE INTO HIGHER
AMPLITUDE FLOW BY LATE IN THE WEEKEND. THIS COULD RESULT IN A RETURN
TO A WETTER PATTERN FOR CENTRAL AND EASTERN IL NEXT WEEK. HOWEVER...
DUE TO SOME MODEL UNCERTAINTY WITH THE SPECIFICS OF THIS TRANSITION
THE UNCERTAINTY LEVEL IS HIGH.

IN THE SHORTER TERM...SHORTWAVE TROUGHING IS EXPECTED TO ROTATE INTO
THE GREAT LAKES REGION FROM THE NW...ALLOWING A WEAK FRONT TO MOVE
TOWARD CENTRAL IL BY LATE TOMORROW AFTERNOON. THIS BOUNDARY WILL
PROVIDE THE FOCUS FOR A FEW THUNDERSTORMS. HOWEVER...WEAK
INSTABILITY/LOW LEVEL MOISTURE LEVELS WILL RESULT IN FAIRLY
ISOLATED COVERAGE FROM LATE AFTERNOON INTO THE EVENING HOURS. WILL
STICK WITH SLIGHT CHANCE POPS FOR THIS POTENTIAL. OTHERWISE...A
WEST WIND AND GENERALLY AMPLE SUNSHINE SHOULD GIVE US HIGHS IN THE
UPPER 80S FRI.

SOMEWHAT DRIER AIR WILL FILTER INTO OUR REGION SATURDAY RESULTING IN
PLENTY OF SUN AND TEMPERATURES IN THE MID TO UPPER 80S. AN
INCREASING LOW LEVEL WIND FIELD SATURDAY NIGHT SHOULD RESULT IN AT
LEAST SCATTERED ELEVATED CONVECTION IN THE ILLINOIS RIVER VALLEY AND
POSSIBLY AS FAR EAST AS BMI. BETTER CHANCES FOR RAIN ACROSS
CENTRAL AND EASTERN IL LOOK TO BE SUNDAY AS MCS REMNANTS FROM OUR
WEST MOVE INTO THE AREA. THE PRESENCE OF SCATTERED THUNDERSTORMS
AND ASSOCIATED CLOUDS SHOULD KEEP TEMPERATURES DOWN IN THE LOWER
TO MID 80S FOR SUNDAY.

FORECAST UNCERTAINTY STARTS TO PLAY A ROLE FROM LATER MONDAY THROUGH
MIDWEEK AS MODEL INCONSISTENCIES AND DIFFERENCES APPEAR. THE GFS IS
MUCH FARTHER EAST WITH THE UPPER TROUGH AXIS THAN THE EUROPEAN
MODEL. THEY BOTH SHOW A FRONT SLOWLY APPROACHING AND EVENTUALLY
MOVING THROUGH ILLINOIS. HOWEVER THE GFS IS QUICKER AND THE EUROPEAN
MUCH SLOWER BECAUSE OF THEIR RELATIVE POSITIONS OF THE EASTERN UPPER
TROUGH AXIS. THIS BOUNDARY WOULD SERVE AS THE FOCUS FOR PERIODS OF
SHOWERS AND T-STORMS MUCH OF NEXT WEEK. WILL LEAN TOWARD A BLEND OF
THESE TWO MODELS FOR THE FORECAST NEXT WEEK. HOWEVER...CONFIDENCE IS
LOW AS THE PATTERN EVOLVES AND THE MODELS DEAL WITH CONSISTENCY
ISSUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNET TO NEAR 5 KTS.

&&

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

&&

$$

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



000
FXUS63 KILX 310506
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1206 AM CDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 850 PM CDT THU JUL 30 2015

QUIET WEATHER CONDITIONS WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
BRINGS MOSTLY CLEAR SKIES. LIGHT WESTERLY WINDS WILL CONTINUE AT
MOST LOCATIONS AND LOWS WILL DROP TO AROUND THE MID 60S. NO FOG
EXPECTED AS MOISTURE DEPTH REMAINS SHALLOW AND LIGHT WINDS SHOULD
PROMOTE VERTICAL MIXING. NO SIGNIFICANT UPDATES NEEDED THIS
EVENING AS FORECASTS REMAIN ON TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 322 PM CDT THU JUL 30 2015

ASIDE FROM A FEW HIGH/THIN CLOUDS DRIFTING ACROSS MAINLY THE
SOUTHERN KILX CWA THIS AFTERNOON AND EVENING...SKIES WILL BE CLEAR
ACROSS CENTRAL ILLINOIS THROUGH TONIGHT.  WINDS WILL BECOME WESTERLY
AND DIMINISH TO 5 MPH OR LESS AFTER SUNSET...WHILE OVERNIGHT LOW
TEMPERATURES DROP INTO THE LOWER TO MIDDLE 60S.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 322 PM CDT THU JUL 30 2015

BROAD UPPER LEVEL RIDGING IN THE WESTERN HALF OF THE COUNTRY AND
BROAD UPPER LEVEL TROUGHING IN THE EAST WILL EVOLVE INTO HIGHER
AMPLITUDE FLOW BY LATE IN THE WEEKEND. THIS COULD RESULT IN A RETURN
TO A WETTER PATTERN FOR CENTRAL AND EASTERN IL NEXT WEEK. HOWEVER...
DUE TO SOME MODEL UNCERTAINTY WITH THE SPECIFICS OF THIS TRANSITION
THE UNCERTAINTY LEVEL IS HIGH.

IN THE SHORTER TERM...SHORTWAVE TROUGHING IS EXPECTED TO ROTATE INTO
THE GREAT LAKES REGION FROM THE NW...ALLOWING A WEAK FRONT TO MOVE
TOWARD CENTRAL IL BY LATE TOMORROW AFTERNOON. THIS BOUNDARY WILL
PROVIDE THE FOCUS FOR A FEW THUNDERSTORMS. HOWEVER...WEAK
INSTABILITY/LOW LEVEL MOISTURE LEVELS WILL RESULT IN FAIRLY
ISOLATED COVERAGE FROM LATE AFTERNOON INTO THE EVENING HOURS. WILL
STICK WITH SLIGHT CHANCE POPS FOR THIS POTENTIAL. OTHERWISE...A
WEST WIND AND GENERALLY AMPLE SUNSHINE SHOULD GIVE US HIGHS IN THE
UPPER 80S FRI.

SOMEWHAT DRIER AIR WILL FILTER INTO OUR REGION SATURDAY RESULTING IN
PLENTY OF SUN AND TEMPERATURES IN THE MID TO UPPER 80S. AN
INCREASING LOW LEVEL WIND FIELD SATURDAY NIGHT SHOULD RESULT IN AT
LEAST SCATTERED ELEVATED CONVECTION IN THE ILLINOIS RIVER VALLEY AND
POSSIBLY AS FAR EAST AS BMI. BETTER CHANCES FOR RAIN ACROSS
CENTRAL AND EASTERN IL LOOK TO BE SUNDAY AS MCS REMNANTS FROM OUR
WEST MOVE INTO THE AREA. THE PRESENCE OF SCATTERED THUNDERSTORMS
AND ASSOCIATED CLOUDS SHOULD KEEP TEMPERATURES DOWN IN THE LOWER
TO MID 80S FOR SUNDAY.

FORECAST UNCERTAINTY STARTS TO PLAY A ROLE FROM LATER MONDAY THROUGH
MIDWEEK AS MODEL INCONSISTENCIES AND DIFFERENCES APPEAR. THE GFS IS
MUCH FARTHER EAST WITH THE UPPER TROUGH AXIS THAN THE EUROPEAN
MODEL. THEY BOTH SHOW A FRONT SLOWLY APPROACHING AND EVENTUALLY
MOVING THROUGH ILLINOIS. HOWEVER THE GFS IS QUICKER AND THE EUROPEAN
MUCH SLOWER BECAUSE OF THEIR RELATIVE POSITIONS OF THE EASTERN UPPER
TROUGH AXIS. THIS BOUNDARY WOULD SERVE AS THE FOCUS FOR PERIODS OF
SHOWERS AND T-STORMS MUCH OF NEXT WEEK. WILL LEAN TOWARD A BLEND OF
THESE TWO MODELS FOR THE FORECAST NEXT WEEK. HOWEVER...CONFIDENCE IS
LOW AS THE PATTERN EVOLVES AND THE MODELS DEAL WITH CONSISTENCY
ISSUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1206 AM CDT FRI JUL 31 2015

VFR CONDITIONS WILL PREVAIL UNTIL EARLY AFTERNOON FRIDAY AS HIGH
PRESSURE PROVIDES CLEAR SKIES AND LIGHT WINDS. A WEAK FRONTAL
BOUNDARY WILL APPROACH FROM THE NORTHWEST TOWARD MIDDAY
FRIDAY. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE FRONTAL
BOUNDARY WITH POTENTIAL FOR LOCAL MVFR CONDITIONS. PREDOMINANT VFR
CONDITIONS STILL EXPECTED...HOWEVER...SO HAVE ONLY INCLUDED VCTS
AND FEW CB IN TAFS AT THIS POINT FROM 19-21Z UNTIL 23-01Z. WINDS
W 3-8 KTS UNTIL FRIDAY AFTERNOON...BECOMING WNW 10-12 KTS WITH
GUSTS TO 18-20 KTS. WINDS DECREASING AROUND SUNET TO NEAR 5 KTS.

&&

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

&&

$$

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



000
FXUS63 KLOT 310323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT THU JUL 30 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST TO NORTHWEST WINDS GUSTING TO AROUND 20 KT ON FRIDAY

KMD

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

HIGH PRESSURE OVER THE REGION...MAINLY CENTERED JUST TO WEST OF
OUR AREA...WILL REMAIN IN PLACE THROUGH THE TAF CYCLE. WEST TO NW
WINDS WILL BE GUSTING INTO THE MID 20 KT RANGE FOR AN HOUR OR TWO
LONGER AND THEN DIMINISH TO LESS THAN 10 KT THIS EVENING. WEST
WINDS THEN BEGIN GUSTING AGAIN INTO THE LOW 20 KT RANGE MID FRIDAY
MORNING THROUGH THE AFTN. A DRY COLD FRONT WILL PASS THROUGH
FRIDAY AFTERNOON WITH A SLIGHT SHIFT TO MORE OF A NW COMPONENT TO
THE WIND IN THE AFTERNOON EARLY EVENING PERIOD. OTHERWISE VFR
CONDITIONS ARE EXPECTED.

KMD

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

* HIGH IN ALL FORECAST ELEMENTS

KMD

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT THU JUL 30 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST TO NORTHWEST WINDS GUSTING TO AROUND 20 KT ON FRIDAY

KMD

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

HIGH PRESSURE OVER THE REGION...MAINLY CENTERED JUST TO WEST OF
OUR AREA...WILL REMAIN IN PLACE THROUGH THE TAF CYCLE. WEST TO NW
WINDS WILL BE GUSTING INTO THE MID 20 KT RANGE FOR AN HOUR OR TWO
LONGER AND THEN DIMINISH TO LESS THAN 10 KT THIS EVENING. WEST
WINDS THEN BEGIN GUSTING AGAIN INTO THE LOW 20 KT RANGE MID FRIDAY
MORNING THROUGH THE AFTN. A DRY COLD FRONT WILL PASS THROUGH
FRIDAY AFTERNOON WITH A SLIGHT SHIFT TO MORE OF A NW COMPONENT TO
THE WIND IN THE AFTERNOON EARLY EVENING PERIOD. OTHERWISE VFR
CONDITIONS ARE EXPECTED.

KMD

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

* HIGH IN ALL FORECAST ELEMENTS

KMD

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT THU JUL 30 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST TO NORTHWEST WINDS GUSTING TO AROUND 20 KT ON FRIDAY

KMD

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

HIGH PRESSURE OVER THE REGION...MAINLY CENTERED JUST TO WEST OF
OUR AREA...WILL REMAIN IN PLACE THROUGH THE TAF CYCLE. WEST TO NW
WINDS WILL BE GUSTING INTO THE MID 20 KT RANGE FOR AN HOUR OR TWO
LONGER AND THEN DIMINISH TO LESS THAN 10 KT THIS EVENING. WEST
WINDS THEN BEGIN GUSTING AGAIN INTO THE LOW 20 KT RANGE MID FRIDAY
MORNING THROUGH THE AFTN. A DRY COLD FRONT WILL PASS THROUGH
FRIDAY AFTERNOON WITH A SLIGHT SHIFT TO MORE OF A NW COMPONENT TO
THE WIND IN THE AFTERNOON EARLY EVENING PERIOD. OTHERWISE VFR
CONDITIONS ARE EXPECTED.

KMD

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

* HIGH IN ALL FORECAST ELEMENTS

KMD

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT THU JUL 30 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST TO NORTHWEST WINDS GUSTING TO AROUND 20 KT ON FRIDAY

KMD

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

HIGH PRESSURE OVER THE REGION...MAINLY CENTERED JUST TO WEST OF
OUR AREA...WILL REMAIN IN PLACE THROUGH THE TAF CYCLE. WEST TO NW
WINDS WILL BE GUSTING INTO THE MID 20 KT RANGE FOR AN HOUR OR TWO
LONGER AND THEN DIMINISH TO LESS THAN 10 KT THIS EVENING. WEST
WINDS THEN BEGIN GUSTING AGAIN INTO THE LOW 20 KT RANGE MID FRIDAY
MORNING THROUGH THE AFTN. A DRY COLD FRONT WILL PASS THROUGH
FRIDAY AFTERNOON WITH A SLIGHT SHIFT TO MORE OF A NW COMPONENT TO
THE WIND IN THE AFTERNOON EARLY EVENING PERIOD. OTHERWISE VFR
CONDITIONS ARE EXPECTED.

KMD

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

* HIGH IN ALL FORECAST ELEMENTS

KMD

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




000
FXUS63 KLOT 310323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT THU JUL 30 2015

.SHORT TERM...
226 PM CDT

THROUGH FRIDAY...

FORECAST PERIOD WILL REMAIN RELATIVELY QUIET...WITH DRY
CONDITIONS EXPECTED. INCREASING WESTERLY WINDS AT THIS TIME WILL
LIKELY REACH THEIR PEAK OVER THE NEXT COUPLE OF HOURS WITH A
DIMINISHING TREND THEN EXPECTED INTO THE EARLY EVENING. A FEW CU
HAVE DEVELOPED THIS AFTERNOON BUT THESE WILL QUICKLY ERODE WITH
CLEAR SKIES EXPECTED ONCE AGAIN TONIGHT. GUIDANCE IS HINTING AT
SOME PASSING MID/HIGH LEVEL CLOUD COVER LATE TONIGHT INTO FRIDAY
MORNING. HOWEVER...FEEL IT MAY BE A BIT AGGRESSIVE AND DONT THINK
IT WILL AMOUNT TO MUCH BEYOND A WINDOW OF PARTLY CLOUDY SKIES.
SUNNY SKIES WILL HELP TEMPS ACROSS THE AREA TO BE SOMEWHAT OF A
MIRROR OF TODAY...WITH OFFSHORE FLOW KEEPING ANY LAKE COOLING
LIMITED ACROSS PORTIONS OF NORTHWEST INDIANA. DEWPOINTS WILL TRY
TO INCREASE THROUGHOUT THE DAY BUT SHOULD BE LIMITED TO THE LOWER
60S BEFORE DAYTIME MIXING ALLOWS DRIER AIR TO MIX DOWN...WITH THIS
LOWER DEWPOINT AIR ALSO LIMITING HEAT INDICES. WAS A LITTLE
CONCERNED THAT PREVIOUS RUNS OF GUIDANCE WERE NOT QUITE HANDLING
PRECIP POTENTIAL FRIDAY AFTERNOON QUITE WELL BUT 12Z GUIDANCE
TODAY HAS CONTINUED A SIMILAR TREND...KEEPING ANY DEVELOPMENT OUT
AHEAD OF APPROACHING TROUGH/BOUNDARY OUTSIDE OF THE CWA. WITH LOW
TO MID LEVEL FLOW ALREADY WEST TO NORTHWEST ON FRIDAY...LOW/MID
LEVEL CONVERGENCE WILL REMAIN RATHER WEAK. ALSO...SUPPORT ALOFT
APPEARS TO BE LACKING. SO HAVE BACKED AWAY ON THUNDERSTORM CHANCES
FRIDAY AFTERNOON FOR THE CWA BUT IF ANY BRIEF/ISOLATED DEVELOPMENT
WERE TO OCCUR...IT WOULD BE ALONG THE FORD/IROQUOIS TO BENTON
COUNTY LINE.

RODRIGUEZ

&&

.LONG TERM...
305 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

MAIN FORECAST CONCERN OVER THE WEEKEND IS CONVECTIVE CHANCES LATE
SATURDAY THROUGH SUNDAY. AFTER A SEASONABLY WARM START TO THE
FIRST WORK WEEK OF AUGUST...THE REST OF NEXT WEEK LOOKS TO BE
COOLER BUT POTENTIALLY ACTIVE AT TIMES. MID AND UPPER LEVEL
PATTERN WILL FEATURE PRIMARILY NORTHWEST FLOW AROUND LARGE
INITIALLY QUASISTATIONARY UPPER LOW NEAR HUDSON BAY THAT WILL
THEN PIVOT SOUTHEAST DURING THE WORK WEEK.

COLD FRONT...ALBEIT WITH NOT MUCH COOLER AIR BEHIND IT...WILL BE
CLEARING SOUTHEAST CWA FRIDAY EVENING. FOCUS FOR ANY CONVECTION
LOOKS TO BE OFF TO EAST AND SOUTHEAST OF THE AREA ASSOCIATED WITH
BETTER CONVERGENCE ALONG THE FRONT. ANTICIPATING MOSTLY CLEAR
SKIES AND NEAR SEASONABLE LOWS. HAVE CONTINUED WITH A DRY
FORECAST FOR SATURDAY DAYTIME HOURS DESPITE SOME MODELS INDICATING
QPF...AS FORCING APPEARS WEAK AND DEWPOINTS COULD BE OVERDONE
LEADING TO TOO MUCH INSTABILITY. 925 MB TEMPS OF +20 TO +22
CELSIUS SUPPORT HIGHS IN MID 80S WITH UPPER 80S POSSIBLE IN
CHICAGO HEAT ISLAND. TIMING OF NEXT COLD FRONT AND UPPER WAVE HAS
SPED UP ON SOME GUIDANCE TO FAVOR EVENING AND OVERNIGHT FOR
SHRA/TSRA CHANCES...WITH MID-HIGH CHANCE POPS NORTH OF INTERSTATE
80. CONFIDENCE IS FAIRLY LOW ON CONVECTIVE EVOLUTION/TIMING...SO
HAVE NOT ADDED TEMPORAL RESOLUTION TO POPS. SPC CURRENTLY HAS A
MARGINAL RISK WEST OF CWA...THOUGH ~40 KT OF DEEP LAYER SHEAR
COULD SUPPORT A THREAT FOR ISOLATED STRONG TO SEVERE STORMS WITHIN
CWA DEPENDING ON MESOSCALE DETAILS.

UPPER WAVE AND ASSOCIATED FORCING APPEARS TO FAVOR SOUTHEAST CWA
FOR HIGHER POPS ON SUNDAY...THOUGH 12Z ECMWF IS MUCH
SLOWER/POSSIBLY AN OUTLIER. DEPENDING ON CLOUD COVER/CONVECTIVE
TRENDS...THERMAL PROGS COULD SUPPORT HIGHS A BIT WARMER THAN
CURRENT FORECAST MID 80S. SIMILAR SITUATION ON MONDAY...AS COLD
FRONT WILL BE MOVING THROUGH BUT VERY WARM THERMAL PROFILES/925 MB
TEMPS IN LOWER-MID 20S CELSIUS COULD YIELD AT LEAST MID-UPPER
80S. HAVE MAINTAINED SLIGHT TO CHANCE POPS FROM BLENDED GUIDANCE
INTO MONDAY NIGHT. UPPER LOW DIVING SOUTHEAST IN THE MID WEEK
PERIOD NEXT WEEK WILL SEND MUCH COOLER AIRMASS THAN WE HAVE BEEN
EXPERIENCING LATELY SOUTHWARD...BUT WITH UNCERTAINTY ON JUST HOW
COOL. CURRENTLY LOOKING AT UPPER 70S-LOWER 80S ON TUESDAY AND
MID-UPPER 70S ON WEDNESDAY AND THURSDAY...ALONG WITH STEADY
ONSHORE WINDS. MODELS ARE OVER THE PLACE ON DAY TO DAY
DETAILS...BUT PERIODIC SLIGHT TO CHANCE POPS SEEM REASONABLE GIVEN
SOMEWHAT DISTURBED NORTHWEST FLOW PATTERN.

RC

&&

.AVIATION...

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

* WEST TO NORTHWEST WINDS GUSTING TO AROUND 20 KT ON FRIDAY

KMD

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

HIGH PRESSURE OVER THE REGION...MAINLY CENTERED JUST TO WEST OF
OUR AREA...WILL REMAIN IN PLACE THROUGH THE TAF CYCLE. WEST TO NW
WINDS WILL BE GUSTING INTO THE MID 20 KT RANGE FOR AN HOUR OR TWO
LONGER AND THEN DIMINISH TO LESS THAN 10 KT THIS EVENING. WEST
WINDS THEN BEGIN GUSTING AGAIN INTO THE LOW 20 KT RANGE MID FRIDAY
MORNING THROUGH THE AFTN. A DRY COLD FRONT WILL PASS THROUGH
FRIDAY AFTERNOON WITH A SLIGHT SHIFT TO MORE OF A NW COMPONENT TO
THE WIND IN THE AFTERNOON EARLY EVENING PERIOD. OTHERWISE VFR
CONDITIONS ARE EXPECTED.

KMD

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

* HIGH IN ALL FORECAST ELEMENTS

KMD

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

* SATURDAY...VFR. WEST WINDS. CHANCE TSRA OVERNIGHT.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. NORTHWEST WINDS.
* TUESDAY...DRY/VFR. NORTHEAST WINDS.
* WEDNESDAY...CHANCE OF TSRA. EASTERLY WINDS.

KMD

&&

.MARINE...
226 PM CDT

OVERALL FLOW OVER THE LAKE HAS DIMINISHED TODAY...BUT WITH
WESTERLY WINDS ALONG THE NEARSHORE IN ILLINOIS INCREASING AT THIS
TIME. THESE INCREASING WESTERLY WINDS WILL LIKELY REACH THEIR PEAK
OVER THE NEXT COUPLE OF HOURS WITH A DIMINISHING TREND THEN
EXPECTED INTO THE EARLY EVENING...WITH THE CURRENT SMALL CRAFT
ADVISORY END TIME STILL ON TRACK TODAY. WESTERLY WINDS OF 10 TO 20
KT WILL LIKELY REMAIN THE GENERAL TREND TONIGHT INTO FRIDAY OVER
THE LAKE...WHILE A TROUGH/FRONTAL BOUNDARY APPROACH ON FRIDAY. OUT
AHEAD OF THESE FEATURES...WEST/NORTHWEST WINDS WILL LIKELY
INCREASE TO THE 20-25KT RANGE BY EARLY FRIDAY AFTERNOON...WITH
HAZARDOUS CONDITIONS FOR SMALL CRAFT BECOMING LIKELY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     FRIDAY TO 7 PM FRIDAY.

&&

$$

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

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




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