Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 260411
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1011 PM CST THU DEC 25 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND FRIDAY
ISSUED AT 308 PM CST THU DEC 25 2014

A WEAK COLD FRONT OVER MINNESOTA ALONG WITH WEAK IMPULSE MOVING
INTO CONFLUENT UPPER FLOW WILL MOVE INTO WI OVERNIGHT AND EARLY
FRIDAY. BAND OF LIGHT SNOW ASSOCIATED WITH WEAK FRONTOGENETIC
FORCING HAS DEVELOPED IN NW WI.

FRONT WILL LIKELY BECOME STATIONARY OVER SOUTHERN WISCONSIN
FRIDAY AS IT BECOMES PARALLEL TO THE UPPER FLOW. BRIEF BREAK FROM
LOW CLOUDS ACROSS FAR SOUTHERN PART OF FORECAST AREA PER SATELLITE
AND LATEST RUNS OF HRRR...BUT MAINLY CLOUDY AS THIS NEXT SYSTEM
MOVES IN. SOME LIGHT SNOW EXPECTED ACROSS THE NORTHWEST HALF OF
THE AREA TONIGHT ASSOCIATED WITH AFOREMENTIONED SYSTEM. FREEZING
DRIZZLE ALSO POSSIBLE A BIT LATER THIS EVENING AS MID LEVEL
MOISTURE IS STRIPPED AWAY. CLOUDS SHOULD HOLD TEMPERATURES UP SO
CONTINUED FORECAST OF SEVERAL DEGREES ABOVE LATEST MOS
GUIDANCE...CLOSE TO MODEL BLEND OF BIAS CORRECTED NUMBERS.

SLIGHT CHANCE FOR A FEW FLURRIES OR FREEZING DRIZZLE FRIDAY
ACROSS ALL BUT FOX VALLEY AND LAKE SHORE. BETTER CHANCE FOR
PRECIPITATION JUST BEYOND THIS FORECAST PERIOD...ASSOCIATED WITH
STRONGER SHORTWAVE/JET MAX THAT EJECTS FROM THE SW U.S. LONGWAVE
TROF AND SURFACE LOW THAT MOVES ALONG FRONT.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY
ISSUED AT 308 PM CST THU DEC 25 2014

FOCUS IN THE LONG TERM WILL BE ON THE SYSTEM MOVING THROUGH GREAT
LAKES REGION FRIDAY NIGHT INTO SATURDAY...WITH PRECIP TYPE ISSUES
IN EAST CENTRAL WISCONSIN AND SNOW ACCUMULATIONS NORTHWEST OF THE
FOX VALLEY.

LOW PRESSURE IS EXPECTED TO DEVELOP IN THE SOUTHERN PLAINS AND
RIDE NORTHEAST ALONG A COLD FRONT. A PROGRESSIVE SHORTWAVE WILL BE
SWINGING THROUGH THE UPPER MIDWEST FRIDAY NIGHT INTO
SATURDAY...WHICH WILL STRENGTHEN THE SFC LOW AS IT SLIPS THROUGH
SOUTHERN WISCONSIN SATURDAY.

TENDED TO USE THE GFS WHEN WORKING WITH THIS SYSTEM...AS IT HAS
HAD THE MOST RUN TO RUN CONSISTENCY...THOUGH MODELS WERE IN
OKAY AGREEMENT WITH MOST ASPECTS OF THE SYSTEM THROUGH THE EVENT
TIME-FRAME. PRECIP SHOULD OVERSPREAD THE AREA AFTER MIDNIGHT
SATURDAY AS WAA/SOUTHWEST FLOW INCREASES AHEAD OF THE MAIN SYSTEM.
THE MAIN SYSTEM PRECIP SHOULD THEN PUSH INTO THE AREA SATURDAY
MORNING...AS THE CENTER OF THE LOW MOVES OVER SOUTHERN WISCONSIN.
AS IT DOES SO...IT WILL SYNC UP WITH A DECENT 500MB SHORTWAVE. THIS
WILL CAUSE THE SFC LOW TO QUICKLY INTENSIFY BEFORE IT SURGES
NORTHEAST INTO LOWER MICHIGAN. PRECIPITATION WILL END WEST TO EAST
AS THE SYSTEM MOVES AWAY FROM THE AREA SATURDAY AFTERNOON...WITH
PRECIP ENDING ALONG THE LAKESHORE 00Z SUNDAY.

PRECIP TYPE MAY BE AN ISSUE IN EASTERN WISCONSIN. PREVIOUSLY
MENTIONED WAA OVERNIGHT FRIDAY WILL CAUSE A WARM LAYER NEAR THE
SFC. WITH NO SNOW COVER WHAT SO EVER OVER THE AREA...IT WONT TAKE
LONG TO RISE ABOVE FREEZING. MODELS IN SOME DISAGREEMENT ON HOW
MUCH WARM AIR WILL BE PRESENT AT THE SFC...WHICH A FEW DEGREES IN
EITHER DIRECTION MAKING THE DIFFERENCE BETWEEN MIX OR ALL SNOW IN
THE EAST. DECIDED TO TREND WITH THE WARMER GUIDANCE...AS MODELS
TEND TO UNDERESTIMATE THE LOW LEVEL WARM LAYER WHEN IT IS THAT
SHALLOW AND TO ACCOUNT FOR THE LACK OF SNOW COVER. THIS WOULD
RESULT IN A RAIN SNOW MIX ALONG THE LAKESHORE FRIDAY NIGHT...WITH
THE MIX PUSHING INLAND THROUGH THE FOX VALLEY SATURDAY MORNING AS
WINDS TURN EAST. DOOR COUNTY SHOULD REMAIN MOSTLY SNOW AS THEY WILL
BE FAR ENOUGH NORTH AND WINDS IN NORTHERN LAKE MICHIGAN DONT VEER
COMPLETELY EAST.

HEAVIEST PRECIP WILL BE THROUGH SATURDAY MORNING AS A SHORTWAVE
SWINGS INTO THE STATE AND FORCING INCREASES. A GENERAL 1 TO 3
INCHES POSSIBLE NORTH AND WEST OF THE FOX VALLEY...WITH LESSER
AMOUNTS SOUTH AND EAST WHERE RAIN WILL MIX WITH SNOW.

AFTER SNOW WINDS DOWN SATURDAY EVENING...QUIET WEATHER CAN BE
EXPECTED INTO NEXT WEEK. AN AMPLIFIED WESTERN RIDGE WILL ALLOW FOR
ARCTIC HIGH PRESSURE TO PUSH DOWN OUT OF CANADA...BRINGING MUCH
COLDER AIR WITH IT. TEMPERATURES WILL BEGIN TO DROP STARTING
SUNDAY...WITH WELL BELOW NORMAL TEMPERATURES EXPECTED BY MIDWEEK.
COLD PATTERN HOLDS TIGHT AND LOOKS TO BE IN PLACE FOR THE
LONG HAUL...WITH BITTERLY COLD TEMPERATURES WELCOMING THE NEW YEAR.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1008 PM CST THU DEC 25 2014

EXPECTED LOW CLD TRENDS HAVE WORKED OUT PRETTY WELL SO
FAR...THOUGH CIGS ACRS THE N HAVE LIFTED SOME. EXPECT THAT TO BE
TEMPORARY...ESP AS BETTER FORCING AND SN SHIFTS N. THE ARRIVAL OF
LOW CLDS IN CENTRAL WL BE DLAD ON THE UPCOMING 06Z TAFS.
&&

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

$$

SHORT TERM.....JKL
LONG TERM......ALLEN
AVIATION.......SKOWRONSKI







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