Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 242317
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
517 PM CST WED DEC 24 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 218 PM CST WED DEC 24 2014

FOG FINALLY LIFTING ACROSS FOX VALLEY...THOUGH VSBY STILL BELOW 1
MI AT ATW EARLY THIS AFTERNOON. OCNL LIGHT RAIN OR DRIZZLE ALSO
PERSISTED IN THE EAST-CENTRAL AS UPPER LEVEL TROF WAS SLOW TO
MOVE THROUGH. LIGHT PRECIP WILL END EARLY AS UPPER TROF EXITS
AREA...THO WILL LINGER SMALL CHANCES NEAR LK MICHIGAN AS MAIN
SURFACE SYSTEM MOVES ACROSS WESTERN OHIO.

WEAK SURFACE AND MID-LEVEL RIDGE BUILDS INTO THE REGION LATER
TONIGHT WITH WINDS TURNING WESTERLY...BUT CLOUDS PERSISTING.
GENERALLY CLOUDY WITH TEMPERATURES IN THE 30S EXPECTED FOR
CHRISTMAS DAY AS SURFACE RIDGE SLOWLY DRIFTS OFF TO THE EAST LATE
IN THE DAY. COULD SEE A FEW BREAKS...BUT SATELLITE IMAGERY SHOWS
A GREAT DEAL OF UPSTREAM CLOUDINESS...AND SHORT-TERM MODEL GUIDANCE
INDICATES CONSIDERABLE BOUNDARY LAYER MOISTURE.

CONFLUENT MID-LEVEL FLOW UPSTREAM OVER THE DAKOTAS WILL RESULT IN BROAD
FRONTOGENETIC FORCING AT LOW TO MID-LEVELS. MODELS ARE PICKING UP
ON THE SIGNAL GENERATE A NARROW BAND OF SNOW ALONG THE
DEFORMATION AXIS FROM SOUTH DAKOTA...EAST ACROSS CENTRAL MINNESOTA
INTO NORTHWEST WISCONSIN.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 218 PM CST WED DEC 24 2014

A FEW THINGS TO FOCUS ON IN THE LONG TERM...BUT NOTHING OF HIGH
IMPACT. FEW WAVES OF ENERGY WITH ASSOCIATED PRECIP THROUGH THE
WEEKEND...THEN TURNING MUCH COLDER.

A DEEP TROUGH WILL BE CENTERED OVER THE WESTERN US AT THE
BEGINNING OF THE LONG TERM...WHICH WILL EXTEND ACROSS INTO THE
NORTHEAST. THIS POSITIVELY TILTED TROUGH WILL REMAIN
FAIRLY STATIONARY THROUGH THE WEEKEND....WITH WAVES OF ENERGY RIDING
UP THROUGH THE FLOW ON THE DOWNSTREAM SIDE OVER THE GREAT LAKES.
SO ISSUES IN THE LONG TERM THROUGH THE START OF NEXT WEEK WILL
REVOLVE AROUND TIMING AND STRENGTH OF THESE IMPULSES THROUGH THE
BROAD FLOW.

MODELS BRING FIRST PIECE OF ENERGY TOWARDS WISCONSIN THURSDAY
NIGHT. ALL MODELS KEEP POPS CONFINED TO NORTHERN WISCONSIN
ASSOCIATED WITH A BROAD AREA OF WEAK FGEN. WHILE FORCING WILL BE
INCREASING OVER THE ENTIRE STATE OVERNIGHT THURSDAY...DRY AIR IN
THE MID- LEVELS SHOULD KEEP THINGS DRY OVER CENTRAL AND EAST
CENTRAL WISCONSIN. WORRIED DRIZZLE OR FREEZING DRIZZLE WILL
DEVELOP IN CENTRAL AND EASTERN WISCONSIN AFTER MIDNIGHT FRIDAY AS FAIRLY
STRONG WAA DEVELOPS IN THE MIDLVLS AND FORCING ALOFT
INCREASES...BUT LEFT IT OUT FOR NOW AS DRY AIR LOOKS VERY DEEP AND
SATURATION NEAR SFC IS RATHER SHALLOW. AGREED WITH MODEL
CONSENSUS AND RAN WITH CHANCE OF LIGHT SNOW ONLY OVER THE NORTH
THURSDAY NIGHT.

MODELS THEN BEGIN TO DISAGREE WITH THE TIMING AND COVERAGE OF
PRECIP STARTING FRIDAY. LEANED TOWARDS THE 12Z GFS/ECMWF AS THEY
WERE THE MOST CONSISTENT FROM THE PREVIOUS RUNS AND WERE THE FIRST
TO PICK UP ON THE STRONGER SOLUTION FOR SATURDAYS SYSTEM.

FRIDAY NIGHT A MORE POTENT LOW WILL EJECT OUT OF THE SOUTHERN
PLAINS AND MOVE TOWARDS STATE AS A SHORTWAVE PUSHES THROUGH THE
UPPER GREAT LAKES. SOME MODELS WANT TO ALLOW PRECIP TO OVERSPREAD
THE AREA ON FRIDAY AS WEAK LOW PRESSURE SWINGS THROUGH THE GREAT
LAKES. WITH INCREASING WAA AND MOISTURE...NO ISSUES GETTING
PRECIP TO FALL HOWEVER PRECIP TYPE MAY BE AN ISSUE WITH SNOW IN
THE NORTH AND RAIN IN EASTERN WISCONSIN FRIDAY AFTERNOON BEFORE
CHANGING BACK TO ALL SNOW FRIDAY NIGHT.

A MORE POTENT SHORTWAVE WILL SWING THROUGH THE AREA FRIDAY NIGHT
AND SATURDAY MORNING. MODELS NOT IN AGREEMENT HOW THIS SYSTEM WILL
BEHAVE SO NAILING DOWN DETAILS AT THIS POINT IS UP IN THE AIR.
MODELS HAVE SLOWED DOWN THIS FEATURE...AND THUS THE ARRIVAL OF
PRECIP. FORCING WOULD SUPPORT PRECIP OVERSPREADING THE AREA LAST
FRIDAY NIGHT...AND THE MAIN PRECIP EFFECTING CENTRAL AND EAST
CENTRAL WISCONSIN SATURDAY MORNING. PRECIP SHOULD THEN DIMINISH
SATURDAY AFTERNOON AS THE SYSTEM QUICKLY EXITS THE AREA...WITH
POPS LINGERING ALONG THE LAKESHORE THE LONGEST INTO SATURDAY
AFTERNOON.

AFTER SATURDAY...A STRENGTHENING WESTERN RIDGE WILL ALLOW ARCTIC
HIGH PRESSURE TO BUILD SOUTH OUT OF CANADA. SO...WHILE QUIET AND
DRY WEATHER CAN BE EXPECTED STARTING SUNDAY...MUCH COLDER AIR WILL
INFILTRATE THE AREA. BELOW NORMAL TEMPS WILL ARRIVE SUNDAY OR
MONDAY...AND BY MID TO LATE NEXT WEEK MUCH OF NE WI WILL BE
STRUGGLE TO GET OUT OF THE SINGLE DIGITS FOR HIGHS. A MARKED
TEMPERATURE DIFFERENCE WILL BE FELT BY TUESDAY.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 513 PM CST WED DEC 24 2014

STILL SOME LINGERING LIFR CIGS OVER E-C WI...OTHERWISE...MAINLY
LOWER-END MVFR CIGS ACRS THE AREA. AS CYCLONE TO OUR E CONTS TO
LIFT AWAY FM THE AREA...EXPECT CONDITIONS OVER E-C WI TO IMPROVE
BACK INTO MVFR CATEGORY. IT WL PROBABLY BE MORE DIFFICULT TO
DISLODGE THE MVFR CIGS HOWEVER...SO EXPECT THOSE TO LINGER THROUGH
TOMORROW.
&&

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

$$

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







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