Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 290910
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
410 AM CDT WED JUL 29 2015

.SHORT TERM...
332 AM CDT

THROUGH TONIGHT...

ONGOING T-STORM ACTIVITY OVER EASTERN CWA ASSOCIATED WITH PRE
FRONTAL TROUGH SHOULD CLEAR THE AREA PRIOR TO SUNRISE. ATTENTION
FOR THE MORNING HOURS WILL TURN WEST TOWARD THE SYNOPTIC FRONT AND
THE POTENTIAL FOR ANY SHOWER AND POSSIBLE T-STORM ACTIVITY WITH
IT. DESPITE RATHER PALTRY APPEARANCE OF PRECIP WITH FRONT AT THIS
TIME...CERTAINLY LESS THAN GUIDANCE WOULD SUGGEST...AM STILL
CONCERNED THAT SOME DEVELOPMENT COULD TAKE PLACE GIVE THE
MAGNITUDE OF MOISTURE AND FORCING WITH FRONT. ANY SCTD SHOWERS AND
POSSIBLE THUNDER SHOULD CLEAR MAJORITY OF THE CWA BY NOON...BUT
SOME ACTIVITY COULD LINGER OR REDEVELOP SOUTH OF KANKAKEE RIVER IN
NW INDIANA EARLY THIS AFTERNOON.

IN WAKE OF THE FRONT DEWPOINTS WILL BEGIN TO TUMBLE...MOST
NOTICEABLY OVER NW HALF OF THE CWA THROUGH MID AFTERNOON WITH
NOTICEABLY LESS HUMID AIR ARRIVING IN CHICAGO METRO AREA BY MID-
LATE AFTERNOON AND IN NW INDIANA EARLY THIS EVENING. AIR MASS NOT
THAT MUCH COOLER BEHIND THE FRONT SO HIGHS SHOULD ONCE AGAIN CLIMB
WELL INTO THE 80S TO PERHAPS NEAR 90 IF THERE IS ENOUGH SUNSHINE.

IZZI

&&

.LONG TERM...
332 AM CDT

THURSDAY THROUGH TUESDAY...

SUNNY AND VERY WARM WEATHER IS ON TAP FOR THURSDAY WITH
COMFORTABLE HUMIDITY LEVELS BY LATE JULY STANDARDS. FRIDAY LOOKS
TO BE A CARBON COPY OF THURSDAY WITH PERHAPS JUST A FEW MORE
CLOUDS BUT STILL A LOT OF SUNSHINE. PROGGED 925MB TEMPS IN THE
LOW-MID 20S CELSIUS SUPPORTS HIGHS IN THE UPPER 80S TO LOWER 90S
AND GIVEN SUCH LOW DEWPOINTS AND AMPLE SUNSHINE HAVE LEANED CLOSER
TO WARMER GUIDANCE BOTH PERIOD.

WEAK COLD FRONT SLIDES THROUGH FRIDAY NIGHT AND CANNOT TOTALLY
RULE OUT SOME ISOLATED CONVECTION WITH IT...THE FACT ITS COMING
THROUGH AT DIURNALLY UNFAVORABLE TIME OF DAY AND WITH NO RETURN
MOISTURE WORK AGAINST INTRODUCING POPS AT THIS TIME. AFTER
COORDINATION WITH MKX IT WAS DECIDED TO KEEP POPS IN THE 10-15
PERCENT RANGE IN THE GRIDS...BELOW MENTIONABLE THRESHOLD IN THE
TEXT FORECAST FOR NOW. A COUPLE OF MORE WEAK NORTHWEST FLOW FRONT
ARE SLATED TO MOVE ACROSS THE CWA SUNDAY AFTERNOON AND TUESDAY
AFTERNOON...BOTH OF WHICH COULD BRING SOME SCATTERED STORMS BUT
NEITHER LOOKING LIKE BIG TIME WASHOUTS FROM WIDESPREAD RAIN
EITHER. FOR NOW HELD ONTO MODEL CONSENSUS LOWER END CHANCE POPS
FOR BOTH FRONTS. NO SIGNIFICANT COOL DOWNS EXPECTED WITH EITHER
FRONT AT THIS TIME.

IZZI

&&

.AVIATION...

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

* SCATTERED SHRA...ISOLATED TSRA THRU MID MORNING.
* POSSIBLE MVFR CIGS THIS MORNING.
* GUSTY WEST/NORTHWEST WINDS TODAY. CMS

//DISCUSSION...UPDATED 09Z...

EARLIER CONVECTION HAS WEAKENED TO SHOWERS/LIGHT RAIN FROM GYY
BACK TO IKK AND PNT. THIS ACTIVITY WILL CONTINUE MOVING TO THE
SOUTHEAST AND AWAY FROM THE TERMINALS. ADDITIONAL CONVECTION HAS
DEVELOPED OVER SOUTH/CENTRAL WI AND ITS POSSIBLE THIS MAY DEVELOP
SOUTHWEST INTO NORTHWEST IL OVER THE NEXT FEW HOURS. IF THAT WERE
TO OCCUR...THAT ACTIVITY WOULD THEN SPREAD EAST LATER THIS
MORNING. CONFIDENCE REGARDING TRENDS IS FAIRLY LOW THOUGH IT DOES
APPEAR THE THREAT OF PRECIP SHOULD BE EAST OF THE TERMINALS BY MID
MORNING. INTRODUCED PRECIP BACK INTO RFD FOR A FEW HOURS AND THEN
MAINTAINED VICINITY MENTION FURTHER EAST...BUT CHANGES ARE
POSSIBLE AS TRENDS EMERGE OVER THE NEXT FEW HOURS. CMS

PREVIOUS 06Z DISCUSSION...

A LINE OF THUNDERSTORMS EXTENDS FROM NEAR DKB SOUTHWEST TO VYS AND
JUST WEST OF PIA. SHORT TERM/HI RES GUIDANCE SEEMS TO HAVE THIS
HANDLED FAIRLY WELL AND CONTINUES TO MOVE IT ACROSS THE AREA EARLY
THIS MORNING. HOW FAR NORTH THIS ACTIVITY WILL SPREAD/DEVELOP IS
STILL UNCERTAIN BUT CLOSE ENOUGH TO INCLUDE TEMPO TSRA AT ALL THE
CHICAGO AREA TERMINALS FOR A FEW HOURS THIS MORNING. HIGH MOISTURE
AIR WILL ALLOW OUTFLOW/GUSTS FROM THESE STORMS TO MAKE IT TO THE
SURFACE...SO SOME GUSTY WINDS WILL BE POSSIBLE WITH THE STRONGEST
STORMS...ALONG WITH TORRENTIAL RAINFALL WHICH MAY BRIEFLY REDUCE
CIGS/VIS TO IFR.

FURTHER WEST...A LARGE AREA OF RAIN WITH EMBEDDED THUNDERSTORMS
LOOKS LIKE IT WILL MAINLY MOVE SOUTHEAST AND SLOWLY WEAKEN SO NOT
COMPLETELY SURE HOW MUCH OF THIS WILL IMPACT THE TERMINALS AROUND
AND AFTER SUNRISE. MAINTAINED VICINITY SHOWERS FOR NOW BUT MAY
END UP BEING DRY.

PATCHY MVFR CIGS HAVE ALREADY DEVELOPED WEST OF THIS CONVECTION
AND EXTEND BACK INTO IA. THERE WILL LIKELY BE A PERIOD OF MVFR
CIGS LATER THIS MORNING...BUT SHOULD BE FAIRLY BRIEF IN
DURATION...PERHAPS ONLY A FEW HOURS AND CONFIDENCE IS LOW
REGARDING SCATTERED VS. BROKEN.

LIGHT SOUTHERLY WINDS TO START WILL SHIFT MORE WESTERLY TOWARD
DAYBREAK WITH SPEEDS SLOWLY INCREASING BUT AS CLOUDS BEGIN TO
SCATTER THIS MORNING AND DRIER AIR SPREADS ACROSS THE REGION...
LOW LEVELS WILL MIX AND WEST/NORTHWEST WINDS WILL INCREASE WITH
GUSTS INTO THE UPPER TEENS...PERHAPS LOW 20KT RANGE...WHICH WILL
THEN DIMINISH WITH SUNSET THIS EVENING. CMS

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

* LOW FOR SCATTERED SHRA/ISOLATED TSRA THRU MID MORNING.
* MEDIUM FOR MVFR CIGS THIS MORNING.
* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH SATURDAY...DRY/VFR. WESTERLY WINDS.
* SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
* MONDAY...CHANCE OF TSRA. LAKE BREEZE POSSIBLE.

KJB

&&

.MARINE...

233 AM...DEEP LOW PRESSURE OVER MANITOBA WILL MOVE NORTHEAST TO
HUDSON BAY THURSDAY AS A TRAILING COLD FRONT MOVES ACROSS THE LAKE
TODAY. SOUTHERLY WINDS 15-25 KTS OVER THE NORTHERN PORTION OF THE
LAKE WILL REMAIN AT THOSE SPEEDS BUT ONLY GRADUALLY TURN WESTERLY
BY THIS EVENING. THIS LOW WILL REMAIN OVER HUDSON BAY THROUGH THE
END OF THE WEEK...WHILE SLOWLY WEAKENING. HIGH PRESSURE WILL BUILD
ACROSS THE CENTRAL PLAINS TODAY AND TONIGHT AND GRADUALLY SPREAD
INTO THE OHIO VALLEY THURSDAY AND FRIDAY. THIS WILL MAINTAIN A
WESTERLY FLOW ACROSS LAKE MICHIGAN WITH PERIODS OF 15-25 KTS
POSSIBLE INTO THURSDAY. THE GRADIENT WILL THEN RELAX WITH SPEEDS
DIMINISHING. A WEAK TROUGH/FRONT WILL MOVE ACROSS THE LAKE FRIDAY
NIGHT...BRIEFLY TURNING WINDS TO THE NORTHWEST BEFORE TURNING BACK
TO THE SOUTHWEST SATURDAY. CMS

&&

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

$$

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