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000
FXUS63 KGRB 021154
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
554 AM CST MON DEC 2 2013

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 401 AM CST MON DEC 2 2013

FCST CONCERNS INCLUDE PCPN TRENDS/TYPE...SNOWFALL ACCUMS AND
TEMPERATURES.

STRATUS CLOUDS REMAINED OVER THE NE HALF OF THE CWA EARLY THIS
MORNING. CLEARING SKIES AND LIGHT WINDS HAVE RESULTED IN PATCHY
FOG DEVELOPMENT OVER THE SW HALF OF THE FA. THE CLEARING SHOULD BE
SHORT-LIVED...AS WIDESPREAD CLOUDS WERE ALREADY SPREADING INTO
WSTRN WI. LIGHT SNOW WAS OCCURRING OVER MUCH OF MN...AND NEARING
THE WI BORDER.

HAVE SIDED WITH THE ECMWF/UKMET MODELS...WHICH ARE FAVORED BY
WPC. OVERALL...THEY OFFER A LESS AMPLIFIED AND COLDER SOLN...
WITH A SFC LOW THAT TRACKS FARTHER SOUTH THAN THE NAM/GFS DURING
THE MIDWEEK PERIOD. FOR THE SHORT-TERM...DYNAMICS WILL BE
PROVIDED BY WAA...AND A S/W TROF MOVG THROUGH TONIGHT.

MODELS ARE IN GOOD GENERAL AGREEMENT THAT PATCHY LIGHT SNOW WILL
MOVE INTO NC/C WI THIS AFTERNOON...WITH DRY AIR IN THE MID-LEVELS
HOLDING OFF PCPN IN EASTERN WI. USED A BLEND OF THE PREV FCST AND
ECMWF FOR TEMPS...RESULTING IN HIGHS IN THE LOWER TO MIDDLE 30S.

THE S/W TROF WILL MOVE THROUGH GRB CWA TONIGHT...CAUSING LIGHT
SNOW TO OVERSPREAD THE REGION DURING THE EVG AND OVERNIGHT.
LINGERING DRY AIR IN FAR NE WI MAY HOLD THE SNOW OFF TIL LATE.
MODELS AGREE THAT A DRY SLOT WILL MOVE INTO THE RGN LATE...
CAUSING THE LIGHT SNOW TO EITHER MIX WITH OR CHANGE OVER TO
FZDZ AFTER 09Z. SNOW ACCUMS SHOULD RANGE FROM NEAR 2 INCHES IN
FAR NC WI...TO AROUND A HALF INCH IN OUR EASTERN COUNTIES.
LOW TEMPS ARE EXPECTED TO BE IN THE MIDDLE 20S TO LOWER 30S.

THE DRY SLOT WILL LINGER INTO TUESDAY MORNING...SO KEPT A MENTION
OF DZ/FZDZ THROUGH 15Z. EXPECT STEADY LIGHT SNOW TO REDEVELOP BY
AFTERNOON...WITH LOW-LEVEL TEMPS AND THICKNESSES INDICATING A MIX
OR CHANGEOVER TO RAIN IN THE SOUTH AND EAST. EXPECT ACCUMS OF 1.5
TO 2 INCHES OVER NC/NE WI...WITH LESSER AMOUNTS SOUTH OF HWY 29.
HIGHS SHOULD BE IN THE LOWER TO MIDDLE 30S.

GIVEN THAT 12-HOUR SNOWFALL AMOUNTS SHOULD BE 2 INCHES OR LESS...
DON`T FEEL THAT A WINTER WX ADVSRY IS WARRANTED AT THIS TIME.
WILL NEED TO WATCH THE TRENDS FOR FZDZ LATE TONIGHT/EARLY TUES...
ALTHOUGH GLAZING IS LESS LIKELY TO BE A PROBLEM WITH A LAYER OF
SNOW ALREADY ON THE ROADS. ROAD CREWS MAY ALREADY BE TREATING
THE ROADS BY THEN TOO.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 401 AM CST MON DEC 2 2013

THE DIFFERENCES THAT HAVE BEEN PLAGUING THE MEDIUM RANGE MODELS
CONTINUE FOR THIS FORECAST CYCLE...AND BEGIN RIGHT OFF THE BAT
TUESDAY NIGHT.  THE NAM/GFS/SREF CONTINUE TO BRING A DEEP/CLOSED
UPPER LOW INTO THE GREAT LAKES WHICH CONSEQUENTLY LEADS TO A STRONG
SURFACE LOW CROSSING NORTHERN WISCONSIN AND THE UPPER PENINSULA.  ON
THE OTHER HAND...THE GEM/UKMET/ECMWF ALL BRING A WEAK/FLAT SHORTWAVE
ACROSS THE REGION.  A WEAK/FLATTER WAVE SEEMS LIKE THE WAY TO
GO...WHICH IS MORE IN LINE WITH THE ECMWF/UKMET SO WILL SIDE WITH
THOSE MODELS FOR THE TUE NIGHT/WED PERIOD.  FOR LATER PERIODS...NOT
SEEING MUCH SUPPORT FOR THE 12Z ECMWF.  UNLESS THE 00Z
CHANGES...WILL LEAN ON THE GFS ENSEMBLE MEAN.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...WEAK AND FLAT SHORTWAVE
ENERGY WILL BE MOVING NORTHEAST ACROSS NORTHERN MINNESOTA/LAKE
SUPERIOR TUESDAY NIGHT.  AHEAD OF THE WAVE...BACKING FLOW IN THE LOW
TO MID LEVELS WILL LEAD A TIGHTENING THERMAL GRADIENT ACROSS
WISCONSIN...WHICH WILL LEAD TO DECENT FGEN DEVELOPING.  MIXING
RATIOS AROUND 3-3.5 G/KG IS ALSO DECENT...AND CONSEQUENTLY BOTH THE
GEM AND UKMET SPIT OUT AROUND 0.25-0.35 INCHES OF QPF TUESDAY
NIGHT.  FORECASTING THE THERMAL GRADIENT REMAINS ONE OF THE BIGGEST
CHALLENGES...BUT WITH FLATTER MID-LEVEL FLOW...TOUGH TO SEE THE 0C
LINE AT 850MB PUSHING INTO NORTHERN WISCONSIN...THOUGH SHOULD SEE A
MIX OR ALL RAIN WORK INTO CENTRAL AND EAST-CENTRAL WISCONSIN.  LOW
PRESSURE WILL THEN MOVE ACROSS THE MID-MISSISSIPPI VALLEY AND INTO
SOUTHERN WISCONSIN OR NORTHERN ILLINOIS ON WEDNESDAY.  A DECENT
SWATH OF PRECIP WILL LIKELY CONTINUE ON THE NORTHERN FLANK OF THE
SURFACE LOW.  COLDER TEMPERATURES ACROSS NORTHERN WISCONSIN WOULD
SUGGEST MAINLY SNOW...WHILE RAIN WILL LIKELY OCCUR OVER CENTRAL AND
NORTHEAST WISCONSIN...THEN WILL HAVE A MIX IN BETWEEN.
CONSEQUENTLY...PUSHED THE ALL RAIN PTYPE FARTHER NORTH ON WEDNESDAY.
ADDITIONAL ACCUMS COULD AMOUNT TO ANOTHER 1-3 INCHES ACROSS THE
NORTHWOODS BRING TOTAL SNOW AMOUNTS TO 2-4 INCHES.  THEN LOW PRESSURE
WILL MOVE INTO LOWER MICHIGAN WEDNESDAY NIGHT THOUGH CONFIDENCE
FALLS WITH PRECIP AMOUNTS/TYPE AT THIS TIME RANGE.  IN ANY
CASE...SEVERAL INCHES OF ACCUMULATING SNOW LOOKS POSSIBLE ACROSS
NORTHERN WISCONSIN DURING THIS PERIOD WHICH MAY REQUIRE A WINTER
HEADLINE THOUGH THE EVENT WILL BE SPREAD OVER A RELATIVELY LONG
DURATION.  DUE TO CONCERNS ABOUT WARM AIR AHEAD OF THE SYSTEM...WILL
NOT ISSUE A HEADLINE AT THIS TIME.

REST OF THE FORECAST...PRECIP WILL BE ENDING LATE WEDNESDAY NIGHT AND
COLDER/DRIER AIR WILL BE PUSHING IN FROM THE WEST.  LOW LEVEL WINDS
ARE A LITTLE TOO WESTERLY FOR LAKE EFFECT SNOWS ACROSS THE SNOW
BELTS DESPITE THE POLAR AIRMASS SURGING INTO THE REGION.  WITH
SOUTHWEST FLOW ALOFT THURSDAY AND FRIDAY...THERE REMAINS A LOW
PROBABILITY THAT A PRECIP BAND COULD PUSH INTO THE REGION FROM THE
SOUTH BUT CONFIDENCE IS TOO LOW TO ADD TO THE FORECAST.  THE REAL
BITTERLY COLD ARCTIC AIR WILL ARRIVE NEXT WEEKEND.  ANY SNOW COVER
FROM THE MID-WEEK STORM WILL GO A LONG WAY IN INSULATING THE
INCOMING ARCTIC AIRMASS AND TEMPS MAY NEED TO GET DROPPED IF THIS
OCCURS.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 540 AM CST MON DEC 2 2013

AN AREA OF MVFR/LOW VFR STRATUS STILL COVERED NE WI EARLY THIS
MORNING...BUT WAS GRADUALLY SHIFTING EAST AND SHRINKING. MID-LEVEL
CLOUDS WERE RAPIDLY APPROACHING FROM THE WEST. WHERE SKIES HAD
CLEARED...PATCHY FOG HAD DEVELOPED.

FOG SHOULD DISSIPATE EARLY...AND CLOUDS WILL GRADUALLY THICKEN
DURING THE DAY. SCT LIGHT SNOW IS EXPECTED TO DEVELOP OVER
NC/C WI DURING THE AFTERNOON. THE SNOW SHOULD BECOME STEADIER
AND GRADUALLY OVERSPREAD THE REGION THIS EVG. A DRY SLOT WILL
ARRIVE LATE TONIGHT...CAUSING THE SNOW TO MIX WITH OR CHANGE
OVER TO FREEZING DRIZZLE. WIDESPREAD MVFR/IFR CONDITIONS SHOULD
PREVAIL AFTER THE STEADY PCPN ARRIVES. SOME LLWS IS EXPECTED TO
DEVELOP AT RHI/AUW/CWA THIS EVG...AND CONTINUE FOR MOST OF THE
NIGHT.

&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......MPC
AVIATION.......KIECKBUSCH