Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 161954
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
254 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* HIGH FOR ALL ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

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

$$

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