Area Forecast Discussion
Issued by NWS Chicago, IL

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348
FXUS63 KLOT 102333
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
533 PM CST WED FEB 10 2016

.SHORT TERM...

TONIGHT AND THURSDAY...

248 PM...ONLY CONCERN IS LIGHT LAKE EFFECT SNOW SHOWERS IN FAR
NORTHEAST PORTER COUNTY.

A RIDGE AXIS EXTENDS FROM MN SOUTHEAST TO CENTRAL IL THIS
AFTERNOON AND WILL SLOWLY TURN EASTERLY AS IT BUILDS ACROSS THE
OHIO VALLEY THURSDAY. CURRENT WAVE WITH LIGHT SNOW OVER PARTS OF
IA INTO SOUTHWEST IL WILL REMAIN SOUTHWEST OF THE CWA. WEST/
NORTHWEST WINDS WILL MAINTAIN THE CHANCE OF LAKE EFFECT SNOW
SHOWERS OVER FAR NORTHEAST PORTER COUNTY TONIGHT WITH MINOR NEW
ACCUMULATIONS POSSIBLE. THESE WILL BEGIN TO DIMINISH THURSDAY AS
WINDS TURN MORE WESTERLY. LOW TEMPS TONIGHT WILL DIP INTO THE LOW
SINGLE DIGITS WITH THE USUAL COLD SPOTS POSSIBLY DIPPING BELOW
ZERO. THESE TEMPS WILL COMBINE WITH NORTHWEST WINDS TO ALLOW WIND
CHILL VALUES 10 BELOW ZERO. CMS

&&

.LONG TERM...

THURSDAY NIGHT THROUGH WEDNESDAY...

248 PM...FORECAST CONCERNS INCLUDE LIGHT SNOW FRIDAY MORNING...
WIND CHILLS POSSIBLY REACHING ADVISORY CRITERIA SATURDAY MORNING
AND ANOTHER PERIOD OF LIGHT SNOW SUNDAY AFTERNOON/SUNDAY NIGHT.

ANOTHER SURGE OF VERY COLD AIR WILL ARRIVE FRIDAY AFTERNOON INTO
FRIDAY NIGHT AND AHEAD OF THIS SURGE...THERE WILL BE A PERIOD OF
LIGHT SNOW FRIDAY MORNING. THERE IS SOME DIFFERENCES REGARDING HOW
FAR NORTH THIS LIGHT SNOW WILL OCCUR...WITH THE GFS FURTHEST NORTH
AND ACROSS THE ENTIRE AREA. BEST CHANCES FOR LIGHT SNOW ALONG WITH
ANY MINOR ACCUMULATIONS APPEAR TO REMAIN ACROSS THE SOUTHERN CWA
AND MAINTAINED LOW CHANCE POPS FOR NOW. BUT AS TRENDS EMERGE...
HIGHER POPS MAY BE NEEDED DESPITE THE LOW QPF EXPECTED. TEMPS ALSO
APPEAR TO HOLD FAIRLY STEADY THURSDAY NIGHT INTO FRIDAY OR PERHAPS
AN EVENING LOW THEN STEADY OR SLOWLY RISING INTO FRIDAY MORNING.

AS THE COLDER AIR ARRIVES FRIDAY AFTERNOON...TEMPS WILL BEGIN TO
FALL WITH LOWS LIKELY BELOW ZERO ACROSS MUCH OF NORTHWEST IL BY
SATURDAY MORNING AND ONLY LOW SINGLE DIGITS ELSEWHERE. NORTHWEST
WINDS WILL ALSO BECOME STRONG/GUSTY FRIDAY AFTERNOON/EVENING WITH
GUSTS PERHAPS INTO THE 30 MPH RANGE. WIND CHILLS WILL LIKELY FALL
BELOW ZERO BY EARLY FRIDAY EVENING AND INTO THE 15 BELOW TO 25
BELOW ZERO RANGE SATURDAY MORNING.

WHILE THE COLDEST AIR WILL BEGIN TO PUSH EAST OF THE AREA SATURDAY
HIGHS WILL LIKELY STRUGGLE TO REACH THE MID TEENS AND THEN A SHARP
DROP SATURDAY EVENING IS POSSIBLE BUT DEPENDENT ON HOW FAST CLOUD
COVER ARRIVES WHICH MAY THEN KEEP TEMPS STEADY OR EVEN BEGIN TO
SLOWLY RISE EARLY SUNDAY MORNING. REGARDLESS...TEMPS DURING THIS
TIME PERIOD WILL LIKELY BE IN THE SINGLE DIGITS ALONG WITH WIND
CHILLS BELOW ZERO.

A CLIPPER LIKE SYSTEM WILL QUICKLY MOVE INTO THE AREA SUNDAY
AFTERNOON INTO SUNDAY NIGHT. THIS SYSTEM HAS BEEN FAIRLY
CONSISTENT FOR SEVERAL DAYS...BUT NOW APPEARS TO BE IN A WEAKENING
PHASE AS IT ARRIVES. SO WHILE IT WILL BE COLD ENOUGH THAT PRECIP
SHOULD BE ALL SNOW...FAIRLY LOW CONFIDENCE ON QPF AMOUNTS
ESPECIALLY ACROSS THE EASTERN CWA. CURRENT TRENDS WOULD SUGGEST A
FEW INCHES OF ACCUMULATION WOULD BE POSSIBLE...BUT TOO EARLY FOR
ANY SPECIFICS. TEMPS LOOK TO RISE BACK INTO THE LOW/MID 20S SUNDAY
AND THEN MAY REMAIN GENERALLY STEADY SUNDAY NIGHT INTO MONDAY
MORNING.

MONDAY AND TUESDAY APPEAR GENERALLY DRY WITH A PERIOD OF RAIN OR
SNOW POSSIBLE LATE TUESDAY NIGHT/WEDNESDAY AS WARMER AIR SPREADS
BACK INTO THE REGION THOUGH DIFFERENCES REMAIN BETWEEN THE
ECMWF/GFS. CMS

&&

.AVIATION...
FOR THE 00Z TAFS...

NO SIG CHANGES TO THE GOING FORECAST. FAIRLY QUIET FOR THE AREA
TERMINALS THROUGH TOMORROW. DIURNAL CU/STRATOCU SHOULD DISSIPATE
WITH SUNSET OTHERWISE...CLOUD COVER WILL MAINLY BE BKN CI
ASSOCIATED WITH A STRONG UPPER JET DIVING THROUGH THE MIDDLE
MISSISSIPPI VALLEY. SFC HIGH PRESSURE EXTENDS FROM CNTRL CANADA TO
THE CENTRAL GULF COAST. AS THE AXIS OF THE HIGH PRESSURE MOVES
ACROSS THE TERMINALS TONIGHT...WINDS WILL DIMINISH...AND
EVENTUALLY BACK TO THE WEST/SOUTHWEST THURSDAY. ENHANCED FORCING
UNDER THE UPPER JET STREAM IS HELPING TO GENERATE SOME SNOW
SHOWERS FROM IOWA INTO SOUTHERN ILLINOIS. THE SFC HIGH PRESSURE
WILL MOVE VERY LITTLE THROUGH THE FORECAST PERIOD AND DO NOT
EXPECT ANY OF THE SNOW TO BE ABLE TO SPREAD EAST ENOUGH TO IMPACT
RFD...LET ALONE THE CHICAGO AREA TERMINALS.

KREIN

&&

.MARINE...
202 PM CST

A MODERATELY STRONG NORTH TO NORTHWESTERLY GRADIENT WILL PERSIST
OVER LAKE MICHIGAN THROUGH TONIGHT AHEAD OF A RIDGE THAT STRETCHES
FROM THE NORTHWEST TERRITORIES INTO THE MISSISSIPPI VALLEY.
WINDS OF 30 KT AND FREEZING SPRAY WILL CONTINUE INTO SOME OF THE
OVERNIGHT HOURS THEN SHOULD DIMINISH EARLY THURSDAY AS THE HIGH
INCHES EAST ALLOWING THE GRADIENT TO RELAX. WINDS ALSO BACK TO THE
WEST ON THURSDAY AS THE HIGH BUILDS SOUTH OF LAKE MICHIGAN...THEN
FRESHEN UP AS LOW PRESSURE FORMS OVER ONTARIO. THIS LOW WILL BRING
A REINFORCING SHOT OF COLD AIR SOUTH ON FRIDAY BEHIND A TRAILING
COLD FRONT AND AS A STRONG ARCTIC HIGH BUILDS ACROSS CANADA INTO
THE UPPER MIDWEST. AT LEAST A SHORT WINDOW OF NORTHERLY GALES ARE
EXPECTED BEHIND THE COLD FRONT FRIDAY EVENING OR OVERNIGHT...THEN
WINDS SHOULD GRADUALLY DIMINISH OVER THE WEEKEND AS THE HIGH
BUILDS ACROSS THE GREAT LAKES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM THURSDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 9 AM THURSDAY.

&&

$$

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