Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 270912
AFDLOT

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

.SHORT TERM...
245 AM CST

THROUGH SUNDAY...

WE ARE LIVING ON BORROWED TIME WITH 850 MB TEMPS SITTING ABOVE
ZERO...BUT THAT WILL BE A THING OF THE PAST COME THIS AFTERNOON. BUT
FIRST OFF...LIGHT RAIN/DRIZZLE IN EAST CENTRAL ILLINOIS AND INTO NW
INDY IS ASSOCIATED WITH THE SLIGHTLY BETTER ISENTROPIC LIFT/MOISTURE
ADVECTION.  THIS WILL DRIFT OFF TO THE EAST THIS MORNING AND WILL
GRAZE OUR SE COUNTIES. MEANWHILE A SECOND AREA OF LIGHT RAIN
CONTINUES OVER NORTHWEST/NORTH CENTRAL ILLINOIS CLOSER TO THE NORTHWARD
MOVING LOW AND EASTWARD ADVANCING COLD FRONT. MUCH OF OUR AREA FINDS
ITSELF IN AN AREA OF WEAKER ISENTROPIC LIFT AND A BIT REMOVED FROM
THE FRONTAL INFLUENCE. THEREFORE...EXPECT SCATTERED LIGHT
RAIN/DRIZZLE IN BETWEEN THAT SHOULD BE LESS ORGANIZED THAN THESE TWO
AREAS.

THE SURFACE LOW IN IOWA CONTINUES TO DEEPEN AND PUSH NE TO NORTHERN
LAKE MICHIGAN THIS MORNING. THE BETTER UPPER DYNAMICS WITH THE
FRONT ARE WITH THE SHORTWAVE MOVING THROUGH IOWA...AND THIS HEADS
NORTHWEST OF OUR AREA TODAY AS WELL. ENOUGH FRONTAL CONVERGENCE
EXISTS TO CARRY A LOW POP RAIN MENTION THROUGH THE MORNING THOUGH
MANY AREAS STAY DRY. THE BETTER MID LEVEL FORCING/FRONTOGENESIS
ARRIVES WITH THE FRONT THIS AFTERNOON BUT MOISTURE IS
LACKING...THEREFORE EXPECT A LARGELY DRY AFTERNOON EXCEPT IN NW
INDIANA AND EASTERN PORTIONS OF ILLINOIS. WITH A STRENGTHENING
UPPER JET OVERHEAD...EXPECT BREEZY SOUTHWEST WINDS AHEAD OF THE
FRONT...THEN GUSTY WEST WINDS BEHIND IT. AFTER A PLEASANT WARM UP
THE LAST FEW DAYS...THIS FRONT DOES HAVE SOME KICK TO IT...AND
WHILE THE COLD AIR DOES NOT NECESSARILY COME SCREAMING IN...DO
EXPECT A RETURN TO REALITY AND MORE SEASONAL CONDITIONS.

THE COLD FRONT WILL BE THROUGH TONIGHT. ANY LINGERING PRECIP IN OUR
FAR SE COUNTIES OF NW INDIANA MAY SEE A LIGHT RAIN/SNOW MIX BEFORE
PRECIP ENDS. OTHERWISE HIGH PRESSURE NOSES IN FROM THE WEST BRINGING
GRADUAL CLEARING OVERNIGHT. READINGS OVERNIGHT DROP INTO THE 20S
TO AROUND 30. SUNDAY LOOKS TO BE GENERALLY SUNNY BUT SEASONALLY
COLD AS THE MAIN UPPER LOW PASSES THROUGH SOUTHERN CANADA.

KMD

&&

.LONG TERM...
245 AM CST

SUNDAY NIGHT THROUGH FRIDAY...

STRONGER CANADIAN HIGH PRESSURE...WILL BE KNOCKING AT OUR DOOR ON
SUNDAY NIGHT...AND WILL SEND A WEAK BACK DOOR COLD FRONT DOWN THE
LAKE. THE LEADING EDGE OF THIS SECONDARY SURGE OF COLD AIR WILL
TRIGGER A SIGNIFICANTLY COLDER STRETCH OF WEATHER TO KICK OFF THE
LAST FEW DAYS OF 2014. THERE MAY BE SOME WEAK LAKE EFFECT SNOW
SHOWERS GETTING INTO NE ILLINOIS...OTHERWISE INCREASING CLOUDS AND
COLDER. THEN AS THE TRULY ARCTIC AIR SPILLS IN MONDAY NIGHT...WE MAY
SEE SOME SNOW SHOWERS ALONG THE BAROCLINIC ZONE. MOISTURE IS NOT
IMPRESSIVE WITH THE FRONT...BUT THE COMBINED NE FLOW OFF THE LAKE
WITH MORE SIGNIFICANT INVERSION HEIGHTS AND MUCH COLDER AIR MAY
ALLOW FOR LAKE ENHANCEMENT AND SOME BETTER ACCUMULATION POTENTIAL.

THEN THE CHILL ENSUES FOR SEVERAL DAYS OF HIGHS ON EITHER SIDE OF 20
AND LOWS IN THE SINGLE DIGITS AND TEENS AS WE REMAIN IN NW FLOW. THE
UPSIDE...LIKELY SOME MORE SUN TO ENJOY TO END THE YEAR...AS ANY
SHORTWAVE ENERGY ROTATING THROUGH FROM THE CANADIAN VORTEX WILL
EITHER REMAIN NORTH OR GENERALLY BE WEAK AS THE ONE THAT COMES
THROUGH TUESDAY NIGHT. SOME MODIFICATION TO THE COLD AIR MASS
ARRIVES ON NEW YEARS DAY AND MORE SO FRIDAY AS WE RETURN TO
SOUTHERLY FLOW. AS THIS OCCURS...WILL HAVE TO WATCH IF LOW
PRESSURE THAT CLOSES OFF OVER CALIFORNIA EARLIER IN THE WEEK
PHASES WITH THE NORTHERN STREAM LOW OR REMAINS FARTHER SOUTH AS
THIS WILL HAVE IMPLICATIONS FOR ANY PRECIPITATION CHANCES TOWARD
WEEKS END.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* MVFR CIGS DROPPING TO IFR FOR EARLY THIS MORNING
* STRONG WEST WINDS LIKELY THIS AFTERNOON BEHIND COLD FRONT
* LINGERING MVFR CIGS POSSIBLE THIS AFTERNOON AND POSSIBLY
  TONIGHT

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 09Z...

* LOW-MEDIUM 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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