Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 270759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
159 AM CST SAT DEC 27 2014

.SHORT TERM...
238 PM CST

THROUGH SUNDAY...

AN UPPER LEVEL RIDGE AXIS STRETCHES FROM CUBA UP THE ATLANTIC COAST
WITH THE SURFACE HIGH OVER THE SOUTHEAST U.S.  THE UPPER LEVEL RIDGE
SHIFTS VERY LITTLE THROUGH SATURDAY. A NARROW SURFACE TROUGH EXTENDS
FROM TEXAS THROUGH THE UPPER PENINSULA OF MICHIGAN THIS AFTERNOON. A
CLOSED LOW WILL FORM OVER THE MID MISSISSIPPI VALLEY TONIGHT AND
MOVE OVER NORTHERN IL LATE TONIGHT/EARLY SATURDAY MORNING BEFORE
MAKING IT TO QUEBEC SATURDAY EVENING.  WEAK HIGH PRESSURE THEN
SPREADS OVER THE CWA SUNDAY.

TEMPERATURES CONTINUE TO CLIMB INTO THE UPPER 40S TO LOWER 50S THIS
AFTERNOON WITH THE MAJORITY OF THE CWA RECEIVING AMPLE SUNSHINE.
CLOUD COVER WILL INCREASE THIS EVENING AND OVERNIGHT AS THE LOW
TAKES SHAPE AND MOVES IN.  WITH THE SURFACE LOW PASSING RIGHT
OVERHEAD...THINKING FOG OR DRIZZLE IS PROBABLE ESPECIALLY WEST OF A
MCHENRY TO JOLIET LINE.  ONLY HAVE PATCHY FOG IN THE FORECAST...BUT
COULD SEE VSBYS IN SOME AREAS DROP TO AROUND OR LESS THAN ONE MILE
DUE TO FOG OR DRIZZLE.

RAIN/DRIZZLE MOVES IN FROM SOUTHWEST TO NORTHEAST LATE THIS
EVENING...AND LATEST RAP AND HRRR GUIDANCE INDICATE THE PRECIP WILL
MOVE IN QUICKER THAN PREVIOUSLY THOUGHT. IT LOOKS LIKE A GOOD HIGH
POP/LOW QPF SITUATION. HAVE AN INCREASING POP TREND FROM MIDNIGHT
THROUGH THE EARLY MORNING HOURS AS THE LOW MOVES OVERHEAD.  LIGHT
RAIN SHIFTS EAST SATURDAY AFTERNOON AS THE LOW CONTINUES NORTHEAST.

GUSTY WEST WINDS ARE EXPECTED TOMORROW WITH GUSTS AROUND 30 MPH IN
THE AFTERNOON.  TEMPERATURES WILL ALSO BE FALLING FROM THE LATE
MORNING HOURS ON BEHIND THE LOWS COLD FRONT. HOWEVER AREAS ALONG AND
EAST OF I-55 WILL SEE HIGH TEMPS IN THE MID 40S TO AROUND 50.  TEMPS
FALL INTO THE 20S SATURDAY NIGHT.

LIGHT WINDS SHIFT TO OUT OF THE NORTHWEST OR NORTH SUNDAY WITH DRY
CONDITIONS EXPECTED.  THE COOLER AIR MASS WILL KEEP HIGH TEMPS IN THE
30S...BUT WE SHOULD SEE SOME SUNSHINE.

JEE

&&

.LONG TERM...
238 PM CST

SUNDAY NIGHT THROUGH FRIDAY...

AN UPPER LEVEL LOW WILL SHIFT EAST OVER NORTHERN QUEBEC
SUNDAY...AND A VORTICITY STREAMER ASSOCIATED WITH THE LOW PUSHES
SOUTH THROUGH THE REGION MONDAY. ANOTHER TROUGH AXIS SWINGS THROUGH
WEDNESDAY.  AT THE SURFACE...WEAK HIGH PRESSURE REMAINS OVER THE
REGION SUNDAY NIGHT. A COLD FRONT COINCIDED WITH THE VORT STREAMER
PUSHES THROUGH THE REGION MONDAY. ARCTIC HIGH PRESSURE FOLLOWS THE
COLD FRONT...AND FINALLY SHIFTS SOUTH TO THE GULF STATES THURSDAY.

CLOUDS INCREASE SUNDAY NIGHT AHEAD OF THE COLD FRONT WITH LOW TEMPS
IN THE 20S.  FLURRIES AND LIGHT SNOW ARE EXPECTED ALONG THE COLD
FRONT AS MODELS CONTINUE TO FEATURE A LITTLE QPF. COLD AIR MASSES
SUCH AS THIS ONE CAN USUALLY SQUEEZE OUT ANY MOISTURE LINGERING IN
THE AIR SO HAVE HIGHER POPS WHERE MODELS FEATURED QPF AND FLURRIES
ACROSS THE REST OF THE CWA.  NOT EXPECTING MUCH SNOW ACCUMULATION IF
ANY AT ALL.  NORTH WINDS DOWN THE LAKE MAY RESULT IN LAKE EFFECT
SNOW OVER NW INDIANA MONDAY NIGHT INTO TUESDAY. COULD SEE A COUPLE
TENTHS OF AN INCH OF SNOW.

THE BIGGER IMPACT WILL BE TEMPERATURES. HIGH TEMPS WILL BE IN THE
LOWER 30S MONDAY THEN ONLY IN THE UPPER TEENS TO MID 20S TUESDAY.
LOW TEMPS TUESDAY WILL BE VARY FROM THE SINGLE DIGITS OVER NORTH
CENTRAL IL TO AROUND 10 DEGREES OVER NORTHWEST INDIANA.  BRISK NW
WINDS WILL CREATE BELOW ZERO WIND CHILLS TUESDAY NIGHT INTO WEDNESDAY
MORNING.  THE WHOLE CWA FEELS THE CHILL WEDNESDAY WITH HIGH TEMPS
AROUND 20 DEGREES BUT GUSTY WEST WINDS WILL MAKE IT FEEL LIKE IT IS
IN THE SINGLE DIGITS.

THE CENTER OF THE HIGH SHIFTS SOUTH OF THE REGION THURSDAY ALLOWING
TEMPS TO WARM SLIGHTLY INTO THE UPPER 20S THURSDAY.  LONG RANGE
GUIDANCE THEN FEATURES A LOW PRESSURE SYSTEM MOVING UP THE OHIO
RIVER VALLEY LATE NEXT WEEK. GUIDANCE HAS THE SYSTEM BRINGING US
SNOW OVER THE WEEKEND...SO WILL KEEP AN EYE ON THIS SYSTEM.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR CIGS DEVELOPING OVERNIGHT POSSIBLY DROPPING TO IFR FOR A
  TIME LATE TONIGHT/SATURDAY MORNING
* STRONG WEST WINDS LIKELY SATURDAY BEHIND COLD FRONT
* LINGERING MVFR CIGS POSSIBLE SAT AFTERNOON AND POSSIBLY SAT NIGHT

IZZI

//DISCUSSION...UPDATED 06Z...

LOW PRESSURE OVER EASTERN IOWA WILL TRACK NORTHEAST INTO
WISCONSIN. NOT SEEING A TON OF SUPPORT FOR IFR CIGS AND DRIZZLE
OVERNIGHT WITH NEAREST IFR CIGS STILL IN SOUTHERN MISSOURI...BUT
WAS RELUCTANT TO TOTALLY REMOVE IT GIVEN PRETTY STRONG SIGNAL IN
GUIDANCE FOR A TIME LATE TONIGHT/SAT MORNING. STILL COULD BE A
SHOWER OR TWO AROUND OVERNIGHT...BUT CHANCES LOOK LOW WITH MUCH IF
NOT ALL THE NIGHT NOW LOOKING TO BE DRY. COLD FRONT WILL SWEEP
ACROSS RFD MID-LATE MORNING AND CLEAR CHICAGO TERMINALS MIDDAY
WITH STRONG/GUSTY WESTERLY WINDS DEVELOPING IN THE WAKE OF THE
FRONT. COULD SEE A COUPLE GUSTS OVER 30KT BUT PREVAILING GUSTS IN
THE 23-28KT RANGE APPEARS PRETTY LIKELY UNTIL WINDS BEGIN TO
SUBSIDE AT SUNSET. MVFR CIGS WILL PROBABLY LINGER THROUGH THE
AFTERNOON AND PROBABLY INTO THE EVENING. COULD SEE MVFR CIGS BEGIN
TO SCATTER OUT AFTER MIDNIGHT SAT NIGHT AS LOW LEVEL FLOW BECOMES
MORE ANTICYCLONIC AND MODELS SUGGEST CONSIDERABLE DRYING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW CONFIDENCE IN CIGS
* MEDIUM-HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SUNDAY...VFR. LIGHT W WINDS BECOMING NNE LATE.

MONDAY...SCHC -SHSN. MVFR PSBL. N TO NE WINDS.

TUESDAY...VFR. BREEZY NW WINDS.

WEDNESDAY AND THURSDAY...VFR. BREEZY SW WINDS AT TIMES.

MDB

&&

.MARINE...
158 AM CST

LOW OVER EASTERN IOWA WILL QUICKLY DEEPEN THROUGH THIS EVENING
AS IT TRACKS NORTHEAST ACROSS NORTHERN LAKE MICHIGAN AND
EVENTUALLY OFF INTO QUEBEC. DUE TO THE BRIEF BUT RAPID DEEPENING
AND COLD AIR ADVECTION THIS AFTERNOON THERE COULD BE A VERY BRIEF
WINDOW OF GALES BEHIND THE FRONT FOR AN HOUR OR TWO OVER SOUTHERN
PORTIONS OF THE LAKE. DURATION LOOKS TO BE TOO SHORT FOR GALE
WARNING THOUGH SO NO HEADLINE PLANNED FOR OPEN WATERS. WINDS/WAVES
LOOK TO RAPIDLY SUBSIDE TONIGHT INTO MONDAY BEFORE AN ARCTIC FRONT
BEGINS WORKING SOUTH DOWN THE LAKE MONDAY NIGHT INTO TUESDAY.
TIGHT GRADIENT BEHIND THE FRONT ALONG WITH VERY COLD AIR AND
UNSTABLE CONDITIONS SHOULD ALLOW FOR STRONG NORTHERLIES TO
DEVELOP...POSSIBLY TO NEAR GALE FORCE BEHIND THE FRONT. THAT
SHOULD MARK THE START OF AN ACTIVE PERIOD ON THE LAKE WITH LOW
PRESSURE TRACKING ACROSS CANADA MIDWEEK DRAGGING A FRONT ACROSS
THE LAKE AND TIGHTENING THE PRESSURE GRADIENT AND PROBABLY LEADING
TO A PERIOD OF WESTERLY GALES WEDNESDAY/EARLY THURSDAY TIME FRAME.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ744-LMZ745...10 AM SATURDAY TO 4 AM
     SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...10 AM
     SATURDAY TO 10 PM SATURDAY.

&&

$$

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