Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 270000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
600 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 00Z...

* MVFR CIGS EXPANDING IN COVERAGE THROUGH THE EVENING THEN
  LOWERING TO IFR OVERNIGHT. LIFR POSSIBLE EARLY SATURDAY MORNING.
  IMPROVEMENT TO MVFR TOWARD MIDDAY SATURDAY.

* CHANCE OF LIGHT RAIN/DRIZZLE OVERNIGHT INTO SATURDAY MORNING.

* SOUTH TO SOUTHWEST WINDS BECOME WESTERLY LATE SATURDAY MORNING
  AND BECOME GUSTY INTO THE AFTERNOON. A FEW GUSTS NEAR 30 KT POSSIBLE.

MDB

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

A TROUGH OF LOW PRESSURE REMAINS TO THE NORTH AND WEST OF THE
TERMINALS THIS EVENING WHILE A LOW PRESSURE CIRCULATION BEGINS TO
TAKE SHAPE OVER THE SOUTHERN PLAINS. WIND SPEEDS HAVE QUICKLY
DROPPED OFF OVER THE LAST HOUR OR SO WITH MOST SITES IN THE 4-6
KT RANGE. WITH CLOUD COVER INCREASING AND THE PRESSURE GRADIENT
SOMEWHAT BAGGY THROUGH THE EVENING SPEEDS WILL LIKELY REMAIN UNDER
8 KT IF NOT UNDER 6 KT FOR THE NEXT FEW HOURS. SPEEDS SHOULD
INCREASE MODESTLY OVERNIGHT AS THE DEVELOPING LOW MOVES NORTHEAST
ACROSS EASTERN IOWA.

MVFR CIGS AROUND 025 CONTINUE TO EXPAND IN COVERAGE ACROSS THE
AREA. LARGE GAPS REMAIN HOWEVER SO INTERMITTENT SCT-BKN COVERAGE
IS LIKELY OVER THE NEXT FEW HOURS BEFORE BECOMING MORE OVC. CIG
BASES WILL ALSO LOWER LATER THIS EVENING THROUGH THE OVERNIGHT
WITH IFR DEVELOPING. TIMING OF THE LOWERING MAY NEED TO BE
ADJUSTED AS IT COULD BE A LITTLE QUICK. LIFR CIGS ARE
POSSIBLE...ESPECIALLY AT RFD TOWARD MORNING AS THE LOW PASSES
NEARBY. WINDS WILL SHIFT WESTERLY AS THE LOW AND ATTENDANT COLD
FRONT PASS DURING THE LATE MORNING. THIS WILL BRING SOME LOW LEVEL
DRYING SO CIGS SHOULD IMPROVE TO MVFR. WINDS WILL PICK UP AND
BECOME GUSTY WITH SOME 30 KT GUSTS POSSIBLE INTO THE AFTERNOON.
SPEEDS WILL EASE UP SATURDAY EVENING. CIGS WILL REMAIN MVFR
THROUGH THE AFTERNOON AND MAY PERSIST THROUGH SATURDAY EVENING AS
WELL.

MDB

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

* HIGH CONFIDENCE IN CIG TRENDS. MEDIUM CONFIDENCE IN TIMING
  CHANGE TO AND FROM IFR. LOW CONFIDENCE IN LIFR POTENTIAL.

* MEDIUM-HIGH CONFIDENCE THAT AT LEAST SOME LIGHT RAIN/DRIZZLE
  OCCURS. MEDIUM-HIGH CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE IN SPEED
  DETAILS.

MDB

//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...
324 PM CST

A TROUGH OF LOW PRESSURE MOVING ACROSS THE REGION IS HELPING TO
PROVIDE SIGNIFICANT DIFFERENCES WITH WIND SPEED AND DIRECTION
ACROSS THE ENTIRE LAKE THIS AFTERNOON...AND EXPECT THESE
DIFFERENCES TO REMAIN IN PLACE TONIGHT INTO SATURDAY MORNING.
WHILE SOUTHERLY FLOW REMAINS IN PLACE OVER THE SOUTHERN HALF OF
THE LAKE...SOUTHERLY WINDS OVER THE NORTHERN HALF ARE ALREADY
SLOWLY BECOMING MORE NORTHERLY AS THIS TROUGH MOVES ACROSS THE
LAKE. THIS TREND WILL CONTINUE OVER THE NORTHERN HALF TONIGHT WITH
MORE NORTHERLY WINDS EXPECTED LATER TONIGHT...WHILE SOUTHERLY
WINDS PERSIST OVER THE SOUTHERN HALF. NEW LOW PRESSURE WILL THEN
DEVELOP ALONG THIS TROUGH/BOUNDARY EARLY SATURDAY MORNING AND MOVE
ACROSS THE LAKE SATURDAY. EXPECT SPEEDS TO INCREASE DURING THE DAY
AS WINDS BECOME MORE WESTERLY IN THE AFTERNOON...AND THEN
NORTHWEST IN THE EVENING. EXPECT SPEEDS TO THEN DIMINISH SATURDAY
NIGHT INTO SUNDAY AS THIS LOW DEPARTS AND HIGH PRESSURE BUILDS
ACROSS THE REGION.

RODRIGUEZ

&&

.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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