Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 192210
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
510 PM CDT SUN OCT 19 2014

.DISCUSSION...
152 PM CDT

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON INDICATES A THIN CIRRUS SHIELD OVER
THE REGION...WITH SOME ENHANCEMENT TO THE CLOUD COVER ACROSS
WISCONSIN AHEAD OF A FRONTAL BOUNDARY THAT IS PUSHING FROM WEST TO
EAST ACROSS THE WESTERN GREAT LAKES. SFC RIDGE HAS DRIFTED SOUTHEAST
OF THE FORECAST AREA...WHICH HAS ALLOWED LLVL FLOW TO TURN
SOUTHWESTERLY. BETWEEN THE NEXT RIDGE OF HIGH PRESSURE AND THE
DEPARTING RIDGE...WEAK TROUGHING WILL SLIDE EAST ACROSS THE UPPER
MIDWEST/GREAT LAKES. THIS HAS PRODUCED A BUMP IN THE GRADIENT AND
RESULTED IN BREEZY CONDS THIS AFTN FROM A GOOD MIXED LAYER.

GUIDANCE HAS SLOWED THE ARRIVAL OF THE FRONTAL BOUNDARY
SLIGHTLY...BUT THERE REMAINS SOME CONSISTENCY THAT THE
MOISTURE/PRECIP WILL BE DISPLACED TO THE NORTHEAST OF THE FORECAST
AREA THRU THE OVERNIGHT PERIOD. TEMPS TONIGHT WILL BE WARMER THAN
THE PRIOR NGT WITH LOWS GENERALLY IN THE LOW/MID 40S.

MONDAY THROUGH THURSDAY...
500MB TROUGH AXIS WILL CONTINUE TO PIVOT EAST OF THE REGION BY
MIDDAY MON...HOWEVER THERE DOES APPEAR TO BE SOME WRAP AROUND
MOISTURE TRYING TO SLIDE SOUTH ACROSS THE LAKE AND MAY PRODUCE SOME
SPRINKLES/LGT RAIN FOR NORTHWEST IN. HAVE MAINTAINED A DRY FORECAST
FOR NORTHEAST IL...HOWEVER LATE MON EVE A FEW SPOTTY SHOWERS COULD
SNEAK INTO THE CHICAGO METRO AREA INTO TUE MORNING. OTHERWISE EXPECT
THE FAR WESTERN FORECAST AREA TO REMAIN DRY. THEN BROAD
ANTI-CYCLONIC FLOW ARRIVES AND IS EXPECTED TO REMAIN IN PLACE THRU
THE SECOND HALF OF THE WEEK. TEMPS MON WILL LIKELY BE THE WARMEST IN
THE UPR 50S TO LOW 60S...THEN COOLING INTO THE LOW/MID 50S FOR
TUE/WED/THUR. WITH HIGH PRES POISED TO BE OVERHEAD TUE
NGT-WED-NGT...LOWS IN MANY AREAS COULD EASILY DIP INTO THE MID 30S.

FRIDAY THROUGH NEXT WEEKEND...
ENSEMBLES CONTINUE WITH THE RATHER BENIGN PATTERN INTO THE WEEKEND.
TROUGH DIGS INTO THE SOUTHWEST CONUS...BUT IS PROGGED TO WEAKEN BY
SAT/SUN. HIGH AMPLITUDE RIDGING OVER THE CENTRAL CONUS WILL
GRADUALLY WEAKEN LATE IN THE WEEK...HOWEVER CURRENT GUIDANCE
SUGGESTS THE DRY PATTERN WILL PERSIST INTO AT LEAST SAT. TEMPS WILL
STEADILY RETURN TO NEAR SEASONAL CONDS WITH HIGHS ARND 60 TO THE LOW
60S BY THE WEEKEND.

BEACHLER

&&

.AVIATION...

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

* SOUTHWEST WINDS OCCASIONALLY GUSTING TO AROUND 20 KT THROUGH THE
  EVENING.

MDB

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

WE HAVE SEEN AN EXPANSION OF MVFR CLOUDS FROM THE SOUTH AND WEST
THIS AFTERNOON. AS DAYTIME HEATING CONTINUES THESE CLOUDS ARE
BREAKING UP SOME AS THEY MIGRATE TO THE EAST AND THE BACK EDGE OF
THE BROKEN CLOUDS IS NOW REACHING A LINE FROM KRPJ TO KDKB...THOUGH
THERE WILL LIKELY BE AT LEAST A BRIEF PERIOD THIS AFTERNOON OF
MVFR CIGS FOR THE CHICAGOLAND TERMINALS.

CONCERNS SHIFT TO WIND SPEEDS THIS AFTERNOON AND EVENING AS LOW
PRESSURE SPREADS TO NORTHERN LAKE MICHIGAN AND A MODEST PRESSURE
GRADIENT SETS UP THROUGH NE ILLINOIS AHEAD OF A COLD FRONT. WIND
SPEEDS AT 2000 FT WILL PUSH 40 KT. NORMALLY WE WOULD SEE WINDS
EASE AT THE SURFACE AT NIGHT BUT THINKING THAT WE WILL CONTINUE TO
SEE WIND GUSTS THROUGH THE EVENING...LIKELY EVEN INCREASING OVER
THIS AFTERNOON. IF THEY DON`T SURFACE THEN THERE MAY BE A PERIOD
OF LOW LEVEL WIND SPEED SHEAR. GRADIENT SLACKENS SOME AFTER
MIDNIGHT THEN A COLD FRONT BRINGS A SHIFT TO NW WIND. NAM IS
SUGGESTING A BUNCH OF LOW CLOUDS IN THE MORNING BUT NOT BUYING OFF
ON THAT AT THE MOMENT. KMD

KMD

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

* HIGH CONFIDENCE IN WIND TRENDS...MEDIUM CONFIDENCE IN OCCASIONAL
  GUSTS CONTINUING THROUGH THE EVENING.

MDB

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

MONDAY NIGHT AND TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY THROUGH SATURDAY...VFR.

IZZI

&&

.MARINE...
324 PM CDT

LOW PRESSURE MOVING THROUGH ONTARIO TONIGHT WILL DRAG A COLD
FRONT ACROSS THE LAKE AND TIGHTEN THE PRESSURE GRADIENT THIS
EVENING. GALE FORCE GUSTS ARE POSSIBLE FOR A TIME BUT GENERALLY
WINDS SHOULD STAY BELOW GALE WARNING CRITERIA. A SMALL CRAFT
ADVISORY CONTINUES FOR NEARSHORE WATERS THIS EVENING AND THROUGH
THE EARLY OVERNIGHT HOURS DUE TO STRONG OFFSHORE WINDS...BUT WAVES
SHOULD NOT BE A BIG PROBLEM UNTIL WINDS TURN NORTHWEST AND THEN
NORTH BY LATE MONDAY...INCREASING AGAIN IN A GRADIENT BETWEEN AN
APPROACHING HIGH AND THE SLOWLY DEPARTING LOW. THESE STRONG
NORTHERLY WINDS PERSIST THROUGH TUESDAY AFTER WHICH TIME THE RIDGE
MOVES OVER THE LAKE BRINGING FAIRLY QUIET CONDITIONS.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 3 AM MONDAY.

&&

$$

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