Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 262038
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
238 PM CST FRI DEC 26 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 AIRMASS 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 WINDCHILLS 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 20Z...

* MVFR CIGS DEVELOPING THIS EVENING AND LOWERING TO IFR OVERNIGHT.
* CHANCE OF LIGHT RAIN OR DRIZZLE OVERNIGHT INTO SATURDAY MORNING.
* GUSTY SOUTH/SOUTHWEST WINDS THIS AFTERNOON.
* STRONG/GUSTY WESTERLY WINDS LATE SATURDAY MORNING INTO SATURDAY
  AFTERNOON. CMS

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

A WEAK FRONTAL BOUNDARY EXTENDS FROM NORTHEAST WISCONSIN SOUTHWEST
INTO THE PLAINS. AS THIS BOUNDARY SLOWLY MOVES EAST TODAY...NEW
LOW PRESSURE WILL DEVELOP OVER MISSOURI AND LIFT NORTHEAST ACROSS
NORTHWEST ILLINOIS SATURDAY MORNING AND THEN CONTINUE NORTHEAST
ACROSS LAKE MICHIGAN SATURDAY AFTERNOON. SOUTHERLY WINDS WILL
CONTINUE TODAY AND TONIGHT AHEAD OF THIS LOW WITH SOME GUSTS INTO
THE UPPER TEEN/LOWER 20KT RANGE POSSIBLE THIS AFTERNOON. WINDS
WILL SHIFT TO THE WEST AS THE LOW DEPARTS AND QUICKLY INCREASE
LATE SATURDAY MORNING INTO SATURDAY AFTERNOON...WHEN THERE COULD
BE A FEW HOUR PERIOD OF GUSTS TO 30 KT...BEFORE RELAXING BACK
INTO THE MID 20KT RANGE THROUGH SUNSET SATURDAY EVENING.

CIGS RANGING FROM 2KFT TO 4KFT ARE SPREADING NORTH INTO SOUTHERN
MISSOURI AND SOUTHERN ILLINOIS LATE THIS MORNING. THIS CLOUD COVER
IS EXPECTED TO CONTINUE NORTH ACROSS THE TERMINALS LATE THIS
AFTERNOON INTO THIS EVENING THEN SLOWLY LOWER...EVENTUALLY INTO
IFR OVERNIGHT. OVERALL CONFIDENCE IN THIS TREND IS HIGH BUT THE
TIMING AND SPECIFIC CIGS WILL LIKELY REQUIRE TWEAKS WITH LATER
FORECASTS. AS THE LOW APPROACHES...ITS POSSIBLE THAT CIGS COULD
LOWER INTO LIFR...ESPECIALLY AT RFD. CIGS WILL THEN LIFT INTO MVFR
AS THE LOW DEPARTS AND POSSIBLY BECOME VFR SATURDAY AFTERNOON.

CONFIDENCE REGARDING PRECIP OVERNIGHT INTO SATURDAY MORNING IS
SOMEWHAT LOW. PRECIP AMOUNTS LOOK FAIRLY LIGHT BUT COULD BE A
PERIOD OF VERY LIGHT RAIN OR DRIZZLE. OPTED TO MAINTAIN CURRENT
RAIN/DRIZZLE MENTION FOR NOW. VISIBILITIES WILL ALSO LIKELY LOWER
INTO MVFR AS LOW LEVEL MOISTURE INCREASES AND IF DRIZZLE BECOMES
PREVAILING...IN ADDITION TO THE APPROACHING LOW PRESSURE...VIS
COULD EASILY DROP TO 1-2SM WITH SOME DENSE FOG POSSIBLE. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH FOR CIG TRENDS...MEDIUM FOR TIMING AND SPECIFIC HEIGHTS.
* MEDIUM FOR LIGHT RAIN OR DRIZZLE OVERNIGHT/SATURDAY MORNING.
* HIGH FOR WINDS THRU THE PERIOD...MEDIUM FOR TIMING CHANGES. CMS

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

SATURDAY NIGHT...MVFR CIGS WITH BREEZY NW WINDS.

SUNDAY...VFR.

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

TUESDAY...VFR. GUSTY NW WINDS.

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

KMD

&&

.MARINE...
234 AM CST

HIGH PRESSURE OVER THE SOUTHEAST STRETCHING UP THE ATLANTIC SEABOARD
WILL REMAIN STATIONARY TODAY BEFORE SHIFTING OUT OVER THE ATLANTIC
ON SATURDAY. MEANWHILE A LOW PRESSURE TROUGH AXIS EXTENDS FROM THE
SOUTHERN HIGH PLAINS THROUGH WESTERN WISCONSIN. THE TROUGH AXIS WILL
SHIFT OVER THE NORTHERN HALF OF THE LAKE TODAY WHICH WILL EASE THE
CURRENT GRADIENT OVER THE LAKE THAT IS DRIVING SOME STRONGER
SOUTHERLIES...ESPECIALLY OVER THE SOUTHERN HALF OF THE
LAKE...WHERE WINDS TO 30 KT CAN BE EXPECTED THROUGH MID MORNING. A
SECONDARY LOW MOVING THROUGH THE TROUGH AXIS WILL REACH CENTRAL
LAKE MICHIGAN AFTER DAYBREAK SATURDAY THEN NORTHEAST OF LAKE
HURON SATURDAY NIGHT...DEEPENING AS IT DOES SO. MODEST HIGH
PRESSURE EMERGES BEHIND THIS SYSTEM...BUT WILL DRIVE A PERIOD OF
WESTERLY WINDS TO 30 KT WITH A MODIFIED COLD FRONT. STRONGER HIGH
PRESSURE WILL MOVE OUT OF CANADA BEYOND THIS TIME FRAME...BRINGING
COLDER NORTH- NORTHWESTERLY FLOW OVER THE LAKE WHICH MAY BECOME
GUSTY AT TIMES. BEFORE THE HIGH MOVES INTO THE NORTHERN PLAINS...A
WEAK TROUGH AND COLD FRONT WILL PASS OVER THE LAKE BY
MONDAY...FOLLOWED BY ANOTHER WEAK TROUGH MID-WEEK.

KMD

&&

.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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