Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 120918
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
318 AM CST FRI FEB 12 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

257 PM...FORECAST CONCERNS INCLUDE LIGHT SNOW/FLURRIES TONIGHT...
WINDY FRIDAY AFTERNOON/EVENING AND WIND CHILLS LATE FRIDAY NIGHT/
SATURDAY MORNING.

HIGH PRESSURE CENTERED OVER THE AREA THIS AFTERNOON WILL QUICKLY
MOVE TO THE MID ATLANTIC BY FRIDAY MORNING AS A WEAK UPPER WAVE
OVER PARTS OF THE PLAINS MOVES SOUTHEAST TONIGHT. FOR THE MOST
PART...GUIDANCE APPEARS TO TAKE THE BULK OF THE ACCUMULATING SNOW
WITH THIS WAVE SOUTH OF THE CWA TONIGHT. MAINTAINED LOW CHANCE
POPS FOR THE SOUTHERN CWA AND MENTION OF FLURRIES NORTHERN AREAS.
IF ANY ACCUMULATION WERE TO OCCUR IT WOULD BE ACROSS THE SOUTHERN
THIRD OR SO OF THE CWA AND LIKELY TO BE JUST A DUSTING. TEMPS WILL
LIKELY DIP THIS EVENING BUT THEN EXPECTED TO HOLD STEADY IN THE
TEENS OVERNIGHT.

LOW PRESSURE MOVING ACROSS THE NORTHERN LAKES TONIGHT WILL PUSH A
COLD FRONT SOUTH ACROSS THE AREA FRIDAY AS STRONG ARCTIC HIGH
PRESSURE BUILDS ACROSS THE NORTHERN PLAINS FRIDAY AFTERNOON AND
MOVES ACROSS THE AREA SATURDAY. THE GRADIENT WILL TIGHTEN BEHIND
THIS FRONT AND NORTHWEST WINDS ARE LIKELY TO BE GUSTING INTO THE
30-35 MPH RANGE FRIDAY AFTERNOON INTO FRIDAY EVENING. WIND CHILLS
WILL DROP BELOW ZERO BY SUNSET FRIDAY EVENING AND CONTINUE TO 15
BELOW TO 25 BELOW ZERO BY SATURDAY MORNING AS LOWS DROP TO NEAR
ZERO AND SINGLE DIGITS BELOW ZERO ACROSS NORTHWEST IL. THE COLDEST
WIND CHILLS APPEAR TO BE MAINLY NORTH OF I-80 SATURDAY MORNING AND
IF THESE TRENDS CONTINUE...A WIND CHILL ADVISORY MAY BE NEEDED.
THE COLDEST AIR SLOWLY PUSHES EAST ON SATURDAY AND TEMPS SHOULD
REBOUND INTO THE LOWER/MID TEENS BUT WINDS WILL ALSO BE
DIMINISHING BY AFTERNOON.

LAKE EFFECT SNOW IS CURRENTLY WINDING DOWN AS THE HIGH BUILDS INTO
THE AREA. BUT THE LAKE EFFECT SNOW WILL DEVELOP AGAIN FRIDAY AND
BEGIN AFFECTING PORTER COUNTY BY FRIDAY EVENING AND LIKELY
CONTINUE THROUGH MIDDAY SATURDAY. DURING THIS TIME...AT LEAST A
FEW INCHES OF SNOW IS POSSIBLE ACROSS NORTHEAST PORTER COUNTY BUT
THESE WILL NEED TO BE MONITORED AS THE LAKE EFFECT SETS UP FRIDAY
AFTERNOON/FRIDAY NIGHT. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

257 PM...FORECAST CONCERNS INCLUDE POSSIBLE ACCUMULATING SNOW
SUNDAY INTO SUNDAY NIGHT AND A CHANCE OF LIGHT SNOW TUESDAY INTO
WEDNESDAY.

A FAST MOVING CLIPPER WILL DIVE SOUTHEAST INTO THE MIDWEST
SATURDAY NIGHT AND SUNDAY. ARRIVAL FROM BOTH THE GFS/ECMWF IS JUST
A BIT SOONER. STILL THINK THAT MUCH OF SATURDAY NIGHT WILL BE DRY
BUT GIVEN THE UNCERTAINTY OF ARRIVAL TIME...DIDN/T GET TOO FANCY
WITH TIMING ON SUNDAY...JUST BUMPED POPS UP TO LIKELY. THE GROWTH
ZONE IS FAIRLY DEEP COMBINED WITH SOUTHERLY WINDS HELPING TO
REPLENISH MOISTURE AND THE COLD AIR IS STILL IN PLACE THROUGH MUCH
OF THE EVENT...THUS SNOWFALL AMOUNTS MAY FLUFF UP AT LEAST A FEW
INCHES AND PERHAPS ACROSS NORTHWEST IL...SEVERAL INCHES. THE
NAM/GEM ARE LOWER WITH THEIR QPF AMOUNTS BUT USING A BLEND OF THE
GFS/ECMWF YIELDS A STORMTOTAL QPF OF ROUGHLY 0.2 INCHES AND WITH
AN AVERAGE SNOW RATIO OF 18:1 OR SO...SNOWFALL AMOUNTS 2 TO 4
INCHES ARE POSSIBLE. BUT ITS IMPORTANT TO REMEMBER THAT THIS IS
STILL 60+ HOURS AWAY AND THESE AMOUNTS WILL LIKELY CHANGE.
SOUTHERLY WINDS ALSO APPEAR TO BECOME QUITE GUSTY SO ITS POSSIBLE
THERE COULD BE SOME BLOWING/DRIFTING SNOW.

TEMPS WILL LIKELY DROP QUICKLY SATURDAY EVENING INTO THE LOW
SINGLE DIGITS WITH LIGHT WINDS AND CLEAR SKIES AND THEN LEVEL OFF
AND POSSIBLY BEGIN TO RISE OVERNIGHT...ESPECIALLY WITH CLOUDS
INCREASING. TEMPS REBOUND BACK INTO THE LOW/MID 20S SUNDAY AND
SHOULD THEN REMAIN GENERALLY STEADY SUNDAY NIGHT.

EARLY/MID NEXT WEEK REMAINS A BIT UNCERTAIN AS WELL AS UNSETTLED
WITH PERHAPS ANOTHER CLIPPER SYSTEM TUESDAY INTO WEDNESDAY. TOO
MUCH UNCERTAINTY TO TRY TO PIN DOWN TIMING OR HIGHER POPS...SO FOR
NOW JUST LOW CHANCE POPS. ALSO APPEARS...IF THIS MATERIALIZES...
ANOTHER LOPE OF COLDER AIR WILL SPREAD ACROSS THE AREA MIDWEEK
WITH THE EXPECTED WARM UP DELAYED TO THURSDAY OR FRIDAY. CMS

&&

.AVIATION...
UPDATED FOR THE 09Z TAFS...
GROWING MORE CONFIDENT FOR BETTER PREVAILING SNOW SHOWERS THIS
MORNING ACROSS THE TERMINALS...AS RADAR IMAGERY DEPICTING AN AREA
OF STEADY SNOW PUSHING SOUTHEAST THROUGH WISCONSIN. TIME OF
ARRIVAL AND SHORT TERM GUIDANCE INDICATING SNOW STARTING AROUND
THE TERMINALS IN THE 11-12Z TIME FRAME...AND HAVE INCLUDED THIS
IN THE 9Z TAF UPDATE. LOOKING UPSTREAM...THERE IS SOME LOWER VIS
AROUND 2SM...BUT AM NOT TOO CONFIDENT WITH HOW LOW THE VIS WILL
GO THIS MORNING OVER THE TERMINALS. WILL CONTINUE TO MONITOR AND
LIKELY ADJUST WITH 12Z TAFS. CONFIDENCE IS EVEN LOWER WITH ANY
SNOW ACCUMULATION BUT AT THIS TIME...THINK MAX WOULD BE A TRACE TO
A TENTH OF AN INCH.

FOR THE 06Z TAFS...

CONDITIONS WILL REMAIN QUIET ACROSS THE TERMINAL THROUGH MUCH OF
THE NIGHT AS SFC HIGH PRESSURE REMAINS IN PLACE. A WEAK MID LEVEL
IMPULSE DROPPING SEWD FROM THE NRN PLAINS THROUGH THE MIDDLE
MISSISSIPPI VALLEY WILL BRING INCREASING CLOUD COVER OVERNIGHT AND
A CHANCE FOR SOME LIGHT SNOW OR FLURRIES. THE TRACK OF THE SYSTEM
SHOULD KEEP THE GREATEST CHANCES FOR ANY ACCUMULATING SNOW TO THE
WEST AND SOUTH OF THE TERMINALS...WITH ONLY SOME VERY LIGHT SNOW
SHOWERS OR FLURRIES POSSIBLE FOR THE TERMINALS. WILL MAINTAIN THE
PREVAILING -SN IN UNRESTRICTED VISIBILITY...BUT IT MAY BE MORE
LIKELY THAT ANY LIGHT SNOW COULD BE INTERMITTENT. THE MAIN IMPACT
SHOULD BE MORE WITH CIGS LOWERING INTO MVFR LEVELS RATHER THAN
VSBY RESTRICTIONS. THE MID LEVEL SYSTEM SHOULD PUSH TO THE SOUTH
AND A SURGE OF COLD ARCTIC AIR WILL PUSH ACROSS THE REGION BY LATE
MORNING. EXPECT THAT WINDS WILL SHIFT TO NWLY AND INCREASE THROUGH
THE LATE MORNING AND AFTERNOON HOURS. LATEST INDICATORS SUGGEST
THAT GUSTS UP TO 30KT ARE LIKELY FOR THE AFTERNOON AND INTO THE
EARLY EVENING HOURS. BRISK NWLY WINDS SHOULD PERSIST THROUGH
TOMORROW NIGHT.

KREIN

&&

.MARINE...
215 AM CST

MAIN FORECAST UPDATE WAS TO BRING UP THE START TIME OF THE GALE
AND FREEZING SPRAY WARNINGS...WITH GALES EXPECTED TO START ACROSS
THE NORTH THIS MORNING AND ACROSS THE SOUTH AND NEARSHORE EARLY
THIS AFTERNOON.

WITH LOW PRESSURE TO THE NORTH AND WITH STRONG HIGH PRESSURE
BUILDING EAST/SOUTHEAST JUST TO THE WEST EXPECT SPEEDS TO REALLY
INCREASE TODAY ACROSS THE ENTIRE LAKE. WINDS ARE CURRENTLY THE
STRONGEST OVER THE NORTH HALF OF THE LAKE WHERE WESTERLY WINDS TO
30KT ARE BEING OBSERVED. THERE HAVE BEEN A FEW GALE FORCE GUSTS IN
THIS LOCATION OVERNIGHT AND DO EXPECT THESE GUSTS TO BE POSSIBLE
THIS MORNING. HOWEVER...MORE SUSTAINED GALES WONT ARRIVE UNTIL MID
TO LATE MORNING AND THEN CONTINUE THROUGH TONIGHT...WHILE THE
SOUTH AND NEARSHORE WATERS SEE GALES THIS AFTERNOON INTO TONIGHT.
GALES SHOULD DIMINISH BY LATE TONIGHT INTO EARLY SATURDAY MORNING
BUT WILL NEED TO MONITOR FOR GALES TO POSSIBLY PERSIST A LITTLE
LONGER OVER THE NORTH HALF. WINDS OVER THE ENTIRE LAKE WILL
DIMINISH SATURDAY INTO SATURDAY NIGHT AS HIGH PRESSURE MOVES
ACROSS THE REGION.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND CHILL ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014...MIDNIGHT SATURDAY TO 9 AM
     SATURDAY.

IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779...NOON FRIDAY TO 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745-LMZ777-LMZ779...3
     PM FRIDAY TO 6 AM SATURDAY.

&&

$$

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