Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 201736
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1136 AM CST SAT DEC 20 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.UPDATE...
ISSUED AT 537 AM CST SAT DEC 20 2014

CALLS TO A COUPLE SHERIFF DEPTS IN THE WSTRN PART OF THE FORECAST
AREA INDICATED THAT FREEZING DRIZZLE IS OCCURRING...SO WILL BE
ADDING FREEZING DRIZZLE AND FLURRIES TO THE FCST FOR NORTH CENTRAL
AND CENTRAL WI FOR THIS MORNING.
&&

.SHORT TERM...TODAY...TONIGHT...AND SUNDAY
ISSUED AT 350 AM CST SAT DEC 20 2014

PCPN TRENDS/TYPE AND TEMPERATURES ARE THE MAIN FCST CONCERNS.

HIGH PRESSURE WAS SLOWLY EDGING EAST...WITH DEVELOPING RETURN
FLOW OVER THE WESTERN GREAT LAKES REGION. INCREASING MOISTURE AND
AN APPROACHING UPPER TROF WAS CAUSING CLOUDS TO INCREASE ACROSS
THE FORECAST AREA EARLY THIS MORNING. WEAK RADAR ECHOES WERE
EDGING INTO NC/C WI...BUT LITTLE PCPN WAS NOTED ON WISCONSIN SFC
OBSERVATIONS.

CANNOT RULE OUT SOME VERY LIGHT FLURRIES OR FREEZING DRIZZLE
OVER THE FCST AREA TODAY...BUT SINCE UPPER FORCING IS EXPECTED
TO SPLIT AROUND THE REGION AND WAA WILL BE FOCUSED TO OUR WEST...
HAVE OPTED TO KEEP OUR CURRENT DRY FCST IN PLACE. A BLEND OF THE
TOP PERFORMING GUIDANCE SUPPORTS HIGH TEMPS IN THE UPPER 20S AND
LOWER 30S.

CLOUDY SKIES WILL KEEP TEMPERATURES FROM DROPPING OFF TOO MUCH
TONIGHT...AND MOST PLACES SHOULD HAVE LOWS IN THE LOWER TO
MIDDLE 20S. WAA WILL INCREASE ACROSS NC/C WI LATE TONIGHT...
AND THIS MAY PROVIDE ENOUGH LIFT TO GENERATE PATCHY FREEZING
DRIZZLE...ESPECIALLY IN OUR SW COUNTIES.

WAA WILL STRENGTHEN ACROSS THE REGION ON SUNDAY AS A LOW-LEVEL
JET INCREASES TO 30 TO 35 KTS. A MIX OF FREEZING DRIZZLE AND
LIGHT SNOW IS EXPECTED TO GRADUALLY SPREAD NE DURING THE
MORNING...WITH A MORE WIDESPREAD LIGHT SNOW OCCURING DURING THE
AFTERNOON AS DEEPER SATURATION ARRIVES. A MIX OF RAIN/SNOW IS
POSSIBLE OVER OUR FAR SOUTHERN COUNTIES LATE IN THE DAY. HAVE
INCREASED POPS TO LIKELY OVER MUCH OF CENTRAL AND NORTHEAST
WI...THOUGH SNOW ACCUMULATIONS SHOULD REMAIN UNDER AN INCH.
HIGH TEMPERATURES ARE EXPECTED TO WARM INTO THE LOWER TO MIDDLE
30S.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ISSUED AT 350 AM CST SAT DEC 20 2014

THE LATEST GFS AND ECMWF ENSEMBLE MEANS HAVE SLOWLY BEEN TRENDING
WEST OVER THE PAST 3 DAYS IN REGARDS TO THE STRONG CYCLONE WHICH
MOVES ACROSS THE GREAT LAKES DURING THE MIDDLE OF NEXT WEEK.  THE
00Z OPERATIONAL GFS ALSO FOLLOWED THIS TREND...TRACKING A RAPIDLY
DEVELOPING LOW PRESSURE SYSTEM OVER THE WESTERN LOWER PENINSULA OF
MICHIGAN.  THE ECMWF AND ECMWF ENSEMBLE MEAN ARE STILL EAST OF THIS
TRACK...TAKING THE LOW OVER LAKE HURON.  THESE DIFFERENCES WOULD
HAVE AN ENORMOUS IMPACT ON THE WEATHER CONDITIONS OBSERVED OVER
NORTHEAST WISCONSIN.  WILL TAKE A BLEND OF THE GFS AND ECMWF...WHICH
TAKES INTO ACCOUNT THIS WESTWARD TREND.

SUNDAY NIGHT THROUGH MONDAY NIGHT...WEAK SHORTWAVE ENERGY WILL EXIT
NORTHEAST AWAY FROM THE REGION ON SUNDAY NIGHT...BUT MODELS CONTINUE
TO SHOW WEAK ISENTROPIC LIFT AHEAD OF HEIGHT FALLS OCCURRING OVER
THE NORTHERN MISSISSIPPI VALLEY.  PROGGED SOUNDINGS CONTINUE TO SHOW
SATURATION ISSUES IN THE MID-LEVELS...BUT THIS WOULD JUST LEAD TO A
CHANCE OF FREEZING DRIZZLE...SINCE THE TEMPERATURE PROFILE WILL BE
NEAR OR BELOW FREEZING ACROSS THE REGION.  PERHAPS COULD SEE UP TO
AN INCH OVER N-C WISCONSIN...BUT MOST PLACES SHOULD SEE UNDER AN
INCH.  THE WEAK ASCENT WILL CONTINUE INTO MONDAY.  THE GFS IS
QUICKER BRINGING IN SHORTWAVE ENERGY INTO THE STATE...WHICH IS AT
ODDS WITH MOST GUIDANCE.  PERHAPS COULD SEE A PERIOD OF DRY WEATHER
ON MONDAY IF MID-LEVELS DRY OUT AGAIN...BUT THIS POTENTIAL WOULD BE
GREATER OVER EASTERN WISCONSIN.  ADDITIONALLY...TEMPS SHOULD WARM
ENOUGH FOR A MIX OR ALL RAIN ACROSS THE EAST IF PRECIP WERE TO
OCCUR.  NOT EXPECTING MUCH ACCUMULATIONS IN ANY EVENT.  MUCH BETTER
POTENTIAL FOR PRECIP ON MONDAY NIGHT AS SHORTWAVE ENERGY AND LOW
PRESSURE MOVE INTO THE REGION.  WARM AIR ALOFT WILL CONTINUE TO
SURGE NORTH ACROSS THE STATE...MAKING SNOW AS THE DOMINANT PTYPE
CONFINED TO NORTHERN WISCONSIN.  COULD SEE AN INCH OR TWO THERE.
BUT TEMPS LOOK WARM ENOUGH FOR A MIX OF RAIN AND SNOW OR ALL RAIN
ELSEWHERE.

REST OF THE FORECAST...THE ACTIVE WEATHER WILL CONTINUE ON TUESDAY
AS LOW PRESSURE MOVES ACROSS THE REGION.  WARM AIR WILL REMAIN AN
ISSUE OVER CENTRAL AND NORTHEAST WISCONSIN...BUT STILL THINKING
MAINLY SNOW OVER N-C WISCONSIN WHERE LIGHT SNOW WILL BE ONGOING.
ANOTHER INCH OR TWO LOOK POSSIBLE.  LIGHT PRECIP WILL CONTINUE ON
TUESDAY NIGHT...BUT MAY START TO FEEL THE IMPACTS OF DEEP CYCLONE
LATE IN THE NIGHT AS IT MOVES NORTH.  THIS TREND WILL CONTINUE ON
WEDNESDAY AS THE LOW MOVES ACROSS THE GREAT LAKES.  THE WESTWARD
TREND IN THE MODELS WOULD GIVE A GREATER CHANCE OF WINTRY PRECIP
IMPACTING EASTERN WISCONSIN WEDNESDAY AND WEDNESDAY NIGHT.  IN
ADDITION TO ANY SNOW...NORTHWEST WINDS WILL ALSO BECOME STRONG AND
GUSTY AND CREATE BLOWING/DRIFTING SNOW ISSUES.  TRENDS IN THE
GUIDANCE ARE INCREASING THE POTENTIAL FOR SIGNIFICANT SNOW OVER
EASTERN WISCONSIN DURING THIS PERIOD...SO ANYONE WITH TRAVEL PLANS
WOULD BE ADVISED TO STAY TUNED TO THE LATEST FORECASTS.

ANY SNOW WILL BE PULLING OUT ON THURSDAY WITH WINDS GRADUALLY
DIMINISHING.  ANOTHER CYCLONE COULD IMPACT THE REGION LATE IN THE
WEEK.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1135 AM CST SAT DEC 20 2014

A WIDE RANGE OF CIGS THIS AFTERNOON RANGING FROM IFR OVER CNTRL WI
TO VFR OVER ERN WI. EXPECT CIGS TO SETTLE MAINLY INTO MVFR
CONDITIONS AS A SHORTWAVE MOVES EAST ACROSS SRN SECTIONS OF THE
GREAT LAKES AND A TRAILING SHORTWAVE TROF ALOFT LINGERS OVER THE
WRN GREAT LAKES. ONSET OF WAA TNGT WL BRING BOTH A LOWERING OF
CIGS INTO THE IFR/LOW-END MVFR RANGE AND THE DEVELOPMENT OF PATCHY
FREEZING DRIZZLE AFTER MIDNGT. THIS WAA PATTERN WL CONT INTO
SUNDAY MORNING WITH ADDITIONAL FREEZING DRIZZLE POSSIBLE. AS THE
MID-LEVELS OF THE ATMOSPHERE SATURATES AND ICE CRYSTALS ARE
INTRODUCED INTO THE COLUMN...THE FREEZING DRIZZLE SHOULD
TRANSITION MORE TO LIGHT SNOW BY SUNDAY AFTERNOON. CIGS/VSBYS
SHOULD GENERALLY REMAIN IN THE MVFR RANGE ON SUNDAY.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE.........KIECKBUSCH
SHORT TERM.....KIECKBUSCH
LONG TERM......MPC
AVIATION.......KALLAS





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