Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 300429
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1029 PM CST THU JAN 29 2015

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND FRIDAY
ISSUED AT 223 PM CST THU JAN 29 2015

MAIN FCST ISSUES CENTER AROUND HOW LONG THESE LOW CLOUDS WL HANG
AROUND TNGT...IMPACT ON MIN TEMPS AND MINOR LAKE EFFECT EVENT
ACROSS N-CNTRL WI.

THE 20Z MSAS SFC ANALYSIS SHOWED A BROAD AREA OF LOW PRES OVER THE
ERN GREAT LAKES AND THE QUEBEC/ONTARIO BORDER AND A BROAD AREA OF
HI PRES THAT STRETCHED FROM LAKE WINNIPEG SWD TO THE SRN PLAINS.
IN BETWEEN THESE SYSTEMS...A TIGHT PRES GRADIENT EXISTED ACROSS
THE UPR MIDWEST WITH GUSTS OCCASIONALLY SURPASSING 30 MPH. SOME
SNOW SHWRS OR FLURRIES WERE FOUND ACROSS UPR MI AND NE MN...BUT
THE PCPN HAD PRETTY MUCH ENDED FOR NE WI. VSBL SATL IMAGERY DID
INDICATE SOME BREAKS OR THIN SPOTS IN THE OVERCAST TO OUR NORTH
AND WEST.

THE SNOW SHWR THREAT FOR N-CNTRL WI WL CONT THRU THE EVENING HOURS
AS FAVORABLE TRAJS...HI DELTA-T VALUES AND WEAKENING CYCLONIC FLOW
TO PERSIST. THAT BEING SAID...SNOW ACCUMULATIONS LOOK TO BE MINOR
DUE TO LOWERING INVERSION HEIGHTS TO 3K FT AND LOWERING DENDRITIC
GROWTH ZONE HEIGHTS. THE NW HALF OF VILAS CNTY COULD GET AROUND AN
INCH OF SNOW WITH LESSER AMOUNTS FARTHER SOUTH AND EAST. AN AREA
OF HI PRES IS FCST TO MOVE INTO THE UPR MS VALLEY OVRNGT AND SEND
ENUF DRY AIR INTO WI TO ESSENTIALLY SHUT-OFF THE LAKE EFFECT.
TRYING TO TIME WHEN TO BREAK UP THE LOW CLOUDS REMAINS THE BIGGEST
FCST PROBLEM...ESPECIALLY SINCE IT IS POSSIBLE THAT THE CLOUDS MAY
HOLD TOUGH PER MODEL TIME SECTIONS. SINCE VSBL SATL IS PICKING UP
SOME BREAKS IN THE CLOUDS ALREADY...HAVE REMAINED OPTIMISTIC THAT
WE WL BE ABLE TO GO AT LEAST PARTLY CLOUDY LATER TNGT. OF COURSE...
THE AMOUNT OF CLEARING WL PLAY A LARGE ROLE IN HOW FAR TEMPS DROP
TNGT. THE GUSTY NW WINDS WL DIMINISH OVRNGT AS THE HI PRES
APPROACHES...THUS AT LEAST PARTIAL CLEARING WOULD ALLOW TEMPS TO
PLUNGE. FOR NOW...HAVE MIN TEMPS AROUND ZERO NORTH...5 TO 10 ABOVE
ZERO SOUTH WITH THE WARMER VALUES NEAR LAKE MI.

THIS AREA OF HI PRES PUSHES ACROSS WI FRI MORNING AND BE JUST TO
OUR EAST FRI AFTERNOON. WINDS ARE EXPECTED TO SLOWLY BACK TO THE
SW DURING THE DAY WITH WEAK WAA DEVELOPING ACROSS THE REGION. LOOK
FOR MID AND HI CLOUDS TO STEADILY OVERSPREAD NE WI ON FRI...THUS
MOSTLY CLOUDY SKIES EXPECTED BY LATE IN THE DAY. DESPITE THE WAA...
TEMPS WL BE MUCH COOLER THAN TODAY WITH READINGS ONLY IN THE 15 TO
20 DEG RANGE.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY
ISSUED AT 223 PM CST THU JAN 29 2015

NO MAJOR STORMS IN THE LONG TERM AS UPPER LEVEL FLOW REMAINS W-NW
ACROSS THE WESTERN GREAT LAKES...KEEPING THE GULF OF MEXICO CLOSED
FOR BUSINESS. MAIN FORECAST ISSUES WILL BE WITH TIMING THE BEST
CHANCES FOR LIGHT SNOW (BOTH SYNOPTIC AND LAKE EFFECT) AND COLD
AIR INTRUSIONS.

CLIPPER SYSTEM STILL ON TRACK TO PUSH ACROSS THE NORTHERN GREAT
LAKES FRIDAY NIGHT INTO SATURDAY. THE MAJORITY OF THE SNOW WITH
THIS SYSTEM LOOKS TO STAY NORTH OF THE STATE...CLOSER TO THE
PARENT UPPER TROUGH AND SHORTWAVE. HOWEVER...MODELS DO ADVERTISE A
WEAKER SHORTWAVE ON THE SOUTHERN EDGE OF THE TROUGH CROSSING LAKE
SUPERIOR FRIDAY NIGHT. THIS SHOULD HELP PRODUCE SOME LIGHT SNOW OR
FLURRIES...MAINLY ACROSS NORTHERN WI. LAKE EFFECT SNOW WILL BE
POSSIBLE BEHIND THIS SYSTEM AS 925-850MB WINDS WAVER FROM NW-NE
SATURDAY AND SUNDAY. WITH NO PERSISTENT FAVORABLE FETCH AND
INVERSION HEIGHTS UNDER 3000-4000FT...DO NOT EXPECT A SIGNIFICANT
EVENT FOR NORTH-CENTRAL WI. CURRENT FORECAST HAS THESE SCENARIOS
HANDLED PRETTY WELL...SO NO MAJOR CHANGES PLANNED.

MODELS HAVE COME INTO BETTER AGREEMENT WITH THE WEEKEND STORM
SYSTEM...AND KEEP THE MAJORITY OF THE ACCUMULATING SNOW SOUTH OF
THE CWA...AS HIGH PRESSURE PUSHING SOUTH OF CANADA LOOKS TO WIN
THE BATTLE AND PUSHES THE BAROCLINC ZONE INTO THE OHIO VALLEY.
THIS WILL KEEP THE BEST FRONTOGENETIC FORCING...SYNOPTIC
LIFT...AND MOISTURE SOUTH OF THE CWA. EVEN THE GEM NOW HOLDS THE
PRECIP FROM SOUTHERN WI SOUTHWARD. HAVE REMOVED POPS FROM THE
GRIDS AND WENT DRY FOR SATURDAY NIGHT AND SUNDAY. THE EXCEPTION
WILL BE OVER FAR NORTH-CENTRAL WI AND EAST-CENTRAL WI...WHERE LAKE
EFFECT FLURRIES AND/OR SNOW SHOWERS WILL BE POSSIBLE. WIND
TRAJECTORIES ON LAKE MICHIGAN POINT TO HIGHER CHANCES FOR LAKE
EFFECT ACTIVITY FROM KEWAUNEE SOUTH...ESPECIALLY ON SUNDAY WHEN
WINDS BECOME A LITTLE MORE OUT OF THE NE.

HIGH PRESSURE SETTLES OVER THE WESTERN GREAT LAKES ON MONDAY WITH
DRY BUT COLD CONDITIONS EXPECTED. THE HIGH QUICKLY SHIFTS EAST OF
THE AREA MONDAY NIGHT AS A WEAK SHORTWAVE PUSHING INTO WI. SOME
LIGHT SNOW IS POSSIBLE WITH THIS FEATURE. ANOTHER...POSSIBLY MORE
POTENT...SHORTWAVE AND UPPER TROUGH IS FORECAST TO PUSH ACROSS THE
AREA ON TUESDAY. THIS SYSTEM WILL NEED TO BE WATCHED AS IT COULD
BRING ACCUMULATING SNOW TO THE ENTIRE AREA...BUT MODEL NOT IN THE
BEST AGREEMENT TO INCREASE POPS AT THIS POINT.

TEMPS WILL APPROACH NORMAL ON SATURDAY (20S)...THEN MUCH COLDER
TEMPS ARE EXPECTED FOR MOST OF NEXT WEEK AS SURGES OF COLD/ARCTIC
AIR SPREADS ACROSS THE GREAT LAKES BEHIND EACH WEATHER SYSTEM.
COLDEST PERIODS LOOK TO BE SUNDAY INTO MONDAY...AND TUESDAY
NIGHT INTO THURSDAY.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1027 PM CST THU JAN 29 2015

MAIN AVIATION FORECAST ISSUE CONTINUES TO BE TIMING OF THE
DISSIPATION OF THE LOW CLOUDS. FLOW ACRS LAKE SUPERIOR WL PROBABLY
CAUSE CLDS TO LINGER A LITTLE LONGER THAN FCST BY THE MODELS OVER
THE WRN PART OF THE FCST AREA...BUT LOW-LEVEL SUBSIDENCE WAS
RESULTING IN A DECR IN CLDS IN THE E AS EXPECTED. THE HOLE SHOULD
GRADUALLY EXPAND...WITH N-C WL PROBABLY BE THE LAST AREA TO CLEAR.
&&

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

$$

SHORT TERM.....KALLAS
LONG TERM......BERSCH
AVIATION.......SKOWRONSKI






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