Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 252342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
542 PM CST TUE NOV 25 2014

.SHORT TERM...
231 PM CST

TONIGHT THROUGH WEDNESDAY...
TEMPERATURE INVERSION HAS BEEN ABLE TO HOLD ONTO THE CLOUDS...WITH
A STUBBORN STRATUS LAYER. FORTUNATELY THIS WEDGE OF CLOUDS WAS
SLOWLY SLIDING EAST THIS AFTERNOON...WITH SOME CLEARING TAKING
PLACE ACROSS WESTERN IL AND STRETCHING FURTHER WEST. SFC RIDGE WAS
PUSHING EAST INTO SOUTHERN MO/NORTHERN AR...WHICH PLACED THE
FORECAST AREA IN THE WESTERLY FLOW AT THE SFC. THERE IS SOME
POTENTIAL THAT PATCHY FOG MAY DEVELOP TONIGHT...GIVEN THE SLOWLY
ERODING CLOUD COVER AND DEW POINTS NOT ABLE TO DRY THIS AFTN. THIS
CURRENTLY IS A LOW CONFIDENCE SCENARIO...BUT FELT IT WAS WORTH
MENTIONING. WITH SOME CLEARING LIKELY TO TAKE PLACE IN THE WESTERN
CWFA...TEMPS SHUD LIKELY BE ABLE TO RADIATE INTO THE LOW TEENS
THERE. ELSEWHERE OVERNIGHT LOWS WILL HOVER ARND 18-22.

SFC RIDGE FOR WED WILL STRETCH FROM THE WESTERN GULF NORTH INTO
LOWER MICHIGAN...AND LIKELY BE SLOW TO DEPART THE REGION. THIS HAS
BEEN IMPACTING THE PLACEMENT/MOISTURE WITHIN A WEAK SHORTWAVE DIVING
SOUTHEAST ACROSS THE UPPER MIDWEST FOR WED. GUIDANCE HAS CONTINUED
TO DEMONSTRATE LESS FAVORABLE SETUP FOR LGT SNOW AND ALSO TIMING FOR
LATER WED. HI-RES LOCAL SOLUTION EVEN SUGGESTS FLURRIES LATE WED
AFTN MAY BE THE EXTENT OF ANY PRECIP. WITH AT LEAST SOME
HIGH/MID-LVL CLOUDS...TEMPS MAY AGAIN BE A CHALLENGE. CURRENT
SOLUTIONS POINT TOWARDS HIGHS WARMING INTO THE LOW/MID 30S...BUT
COULD SEE TEMPS STRUGGLING TO WARM BEYOND THE LOW 30S.

WITH THE MID-LVL TROUGH AXIS PIVOTING EAST ACROSS THE FORECAST AREA
WED EVE AND SOME WEAK OMEGA INTO THE MOIST LAYER...SOME LIGHT SNOW
COULD PRODUCE A DUSTING WED EVE BUT THE CONFIDENCE WITH THIS
SCENARIO CONTINUES TO DIMINISH. A FRONTAL BOUNDARY WILL THEN SLIDE
EAST ACROSS THE REGION WED NGT...WITH ANOTHER RIDGE OF HIGH PRESSURE
SLOWLY BUILDING IN FROM THE UPPER MIDWEST.

BEACHLER

&&

.LONG TERM...
231 PM CST

THANKSGIVING THROUGH TUESDAY...
500MB TROUGH WILL BE DEPARTING THE REGION FOR THANKSGIVING...WITH
BROAD SFC RIDGE BUILDING IN FROM THE WEST DURING THE DAY. THIS SHUD
PROVIDE A GRADUAL EROSION TO THE CLOUD COVER. TEMPS WILL HOVER IN
THE MID/UPR 20S...BUT IF CLOUDS CAN ERODE EARLIER THEN TEMPS MAY BE
ABLE TO WARM A DEGREE OR TWO HIGHER.

MID-LVL FLOW BEGINS TO TRANSITION INTO A SEMI-ZONAL SETUP...WITH THE
POTENTIAL FOR ANOTHER LOW PRESSURE SYSTEM BRINGING A CHC FOR LGT
SNOW FRI. ENSEMBLES CONTINUE TO SUGGEST THAT SAT COULD WARM WELL
INTO THE 40S...PERHAPS TOUCHING 50 DEGREES IN THE SOUTHERN CWFA. FOR
THE SECOND HALF OF THE WEEKEND GUIDANCE DIFFERS ON TIMING OF A
FRONTAL BOUNDARY. IF A SLOWER SOLUTIONS OCCURS...SUN COULD ALSO BE A
MILD DAY WITH HIGHS IN THE MID/UPR 40S.

GUIDANCE HAS BEEN SUGGESTING A NARROW BAROCLINIC ZONE MAY DEVELOP
ALONG THE OHIO VALLEY EARLY NEXT WEEK...WHICH COULD KEEP SOME LGT
PRECIP IN THE SOUTHEAST FORECAST AREA.

BEACHLER

&&

.AVIATION...

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

* BRIEF PERIOD OF MVFR CIGS 1600-2000 FT POSSIBLE EARLY THIS
  EVENING.

RATZER

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

WEAK SURFACE HIGH PRESSURE DRIFTING EAST ACROSS ILLINOIS AND
WESTERN INDIANA THIS EVENING. WEST WINDS 5-10 KT EARLY WILL
DIMINISH TO 5 KT OR LESS OVERNIGHT...GRADUALLY BACKING SOUTHWEST
THIS EVENING AND EVENTUALLY TO SOUTHEAST EARLY WEDNESDAY IN
RESPONSE TO AN AREA OF LOW PRESSURE WHICH WILL MOVE FROM THE
DAKOTAS TO THE LOWER OHIO VALLEY. WINDS...WHICH SHOULD REMAIN LESS
THAN 10 KT THROUGH WEDNESDAY...WILL THEN SHIFT NORTHERLY WEDNESDAY
EVENING.

CHICAGO TERMINALS HAVE BEEN WITHIN WESTERN PERIPHERY OF LOW LEVEL
MOISTURE TRAPPED BENEATH AN INVERSION BASED AROUND 2500 FT AGL...
WITH MVFR STRATOCU DECK IN THE 1600-2000 FT RANGE LINGERING MAINLY
SOUTH/EAST OF ORD. THIS DECK WILL CONTINUE TO DRIFT SLOWLY EAST
THIS EVENING MAINLY AFFECTING MDW/GYY THROUGH THE EARLY EVENING
HOURS. EROSION OF THIS DECK AS OCCURRED FARTHER NORTH ACROSS DPA-
ORD SO NOT EXPECTING A CEILING AT THIS TIME. WITH LIGHT WIND
REGIME THERE IS A LOW-PROBABILITY POTENTIAL FOR SOME MVFR SHALLOW
FOG TO DEVELOP MAINLY AWAY FROM CHICAGO METRO TERMINALS LATE
TONIGHT...THOUGH CONFIDENCE IS LOW EN0UGH TO LEAVE OUT OF TAFS AT
DPA AND RFD AT THIS TIME.

VFR CONDITIONS EXPECTED OVERNIGHT AND WEDNESDAY...WITH ONLY
MID/HIGH CLOUDS ASSOCIATED WITH DISTURBANCE PASSING TO THE
SOUTHWEST OF THE FORECAST AREA.

RATZER


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

* MEDIUM-HIGH CONFIDENCE IN NO PERSISTENT MVFR CIG THIS EVE.

* HIGH CONFIDENCE ALL OTHER ELEMENTS.

RATZER

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

THURSDAY...SLGT CHANCE OF MVFR LGT SNOW EARLY...OTHERWISE VFR.

FRIDAY...SLGT CHANCE OF LGT SNOW. MVFR POSSIBLE.

SATURDAY THROUGH MONDAY...PRIMARILY VFR...THOUGH A PERIOD OF MVFR
OR IFR CIGS  POSSIBLE SATAURDAY INTO EARLY SUNDAY.

RATZER

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

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

$$

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