Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 011152
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
652 AM CDT WED APR 1 2015

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 415 AM CDT WED APR 1 2015

TEMPERATURES...PCPN TRENDS...THE THREAT OF TSTMS...AND ELEVATED FIRE
WEATHER CONDITIONS...ARE THE MAIN FCST CONCERNS FOR THE SHORT-TERM PERIOD.

SOUTHERLY RETURN FLOW WAS RAMPING UP OVER THE UPPER MISSISSIPPI VALLEY...
IN ADVANCE OF LOW PRESSURE AND AN ASSOCIATED COLD FRONT OVER THE WSTRN
DAKOTAS. INCREASING WAA WAS PRODUCING SOME VIRGA OR LIGHT SPRINKLES
FROM A 10-12K FT CLOUD DECK OVER NW WI...BUT HAVE NOT SEEN ANY REPORTS
OF PCPN REACHING THE GROUND.

HAVE KEPT SOME LOW-END POPS OVER NORTHERN WI TO ACCOUNT FOR WEAK
ELEVATED CONVECTION DUE TO WAA ASSOCIATED WITH A 45-55 KT LLJ AND
STEEP MID-LEVEL LAPSE RATES TODAY. HOWEVER...THE BEST PCPN CHANCES WILL
CONTINUE TO BE FOCUSED ALONG AND AHEAD OF A COLD FRONT THAT WILL SWEEP
ACROSS THE REGION TONIGHT INTO THURSDAY MORNING. THIS FRONT WILL BE
ACCOMPANIED BY PRECIPITABLE WATER VALUES OF 1.0-1.2 INCHES...H8 LI`S
OF ZERO TO -3 AND UPPER LEVEL SUPPORT FROM THE RRQ OF A 110-120 KT
JET. HAVE MADE MINOR ADJUSTMENTS TO SLOW DOWN TIMING A BIT...BUT
OTHERWISE KEPT LIKELY TO LOW-END CATEGORICAL POPS AND MODERATE QPF
AMOUNTS IN THE FORECAST TONIGHT AND THURSDAY MORNING. HAVE ALSO
KEPT THE CHANCE OF TSTMS IN THE FORECAST DUE TO PREVIOUSLY
MENTIONED ELEVATED INSTABILITY...MOISTURE AND FORCING.

SOUTH WINDS GUSTING TO 25 TO 30 MPH WILL BRING MILD AIR INTO THE
REGION TODAY...WITH TEMPS GETTING INTO THE 50S/60S MOST PLACES...
WITH A FEW READINGS AROUND 70 IN CENTRAL WI AND COOLER UPPER 40S
NEAR LAKE MICHIGAN DUE TO SE WINDS. ALSO RAISED TEMPS INTO THE
LOWER TO MIDDLE 60S ON THURSDAY DUE TO AFTERNOON SUNSHINE AND DEEP
MIXING. WEST WINDS WILL GUST TO 25 TO 35 MPH DURING THE AFTERNOON.

SEE THE FIRE WEATHER SECTION BELOW FOR INFORMATION ON ELEVATED FIRE
DANGER.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 415 AM CDT WED APR 1 2015

MEAN FLOW ACROSS THE GREAT LAKES THRU THIS WEEKEND TO BE FROM THE
NW BEHIND THE PASSAGE OF A CDFNT (THU NGT)...A SHORTWAVE TROF
(FRI) AND THE MOVEMENT OF A CLOSED UPR LOW AROUND HUDSON BAY (FRI-
SUNDAY). THE MEAN FLOW THEN TURNS SW FOR EARLY NEXT WEEK AS A
SUBSTANTIAL UPR TROF MOVES INTO THE WRN CONUS. MAIN FCST CHALLENGE
IS ASSOCIATED WITH THIS UPR TROF AS PIECES OF ENERGY EJECT NEWD
THRU THE CNTRL CONUS AND INTERACT WITH A QUASI-STNRY FNT DRAPED
FROM THE CNTRL PLAINS TO THE EAST COAST. WHILE TEMPS OVER NE WI WL
WARM A BIT...THIS PATTERN WL LEAD TO A STRETCH OF UNSETTLED
WEATHER WITH SEVERAL CHCS FOR PCPN.

SECONDARY CDFNT SWEEPS THRU WI THU NGT WITH A GRADUAL WIND SHIFT
FROM THE WEST TO THE N-NW. LITTLE MOISTURE LEFT BEHIND OVER THE
REGION AFTER THE PASSAGE OF THE FIRST CDFNT (WED NGT)...THUS NO
PCPN MENTIONED IN THE FCST FOR MOST OF THE FCST AREA. THE
EXCEPTION WOULD BE VILAS CNTY WHERE LAKE EFFECT SNOW SHWRS AND/OR
FLURRIES ARE POSSIBLE AS CAA PUSHES INTO WI. 8H TEMPS OVER WRN
LAKE SUPERIOR DROP TO AROUND -12C BY 12Z FRI AND WITH FAVORABLE
TRAJS...CANNOT RULE OUT A LITTLE LIGHT SNOW. DELTA-T VALUES ARE
ONLY IN THE LWR TEENS...THUS DO NOT ANTICIPATE MUCH (IF ANY)
ACCUMULATION. MIN TEMPS TO RANGE FROM THE MID TO UPR 20S N-CNTRL...
MID 30S E-CNTRL WI.

A TRAILING WEAK SHORTWAVE TROF TO MOVE INTO THE WRN GREAT LAKES ON
FRI...BUT WITH LITTLE FORCING OR LIFT EVIDENT...THIS FEATURE SHOULD
ALSO PASS THRU WITH LITTLE FANFARE. THE LAKE EFFECT THREAT ACROSS
VILAS CNTY WL REMAIN MARGINAL THRU FRI MORNING AND BECOME EVEN LESS
FAVORABLE FRI AFTERNOON AS A RDG OF HI PRES BUILDS ACROSS THE UPR
MS VALLEY AND SENDS DRIER AIR INTO WI. MAX TEMPS WL REMAIN BELOW
NORMAL WITH READINGS ONLY REACHING THE UPR 30S TO LWR 40S NORTH AND
THE LAKESHORE...MID TO UPR 40S SOUTH.

THE SFC RDG SLIDES ACROSS WI FRI EVENING AND ALREADY BE HEADED
TOWARD THE ERN GREAT LAKES BY DAYBREAK. HOT ON THE HEELS OF THIS
SFC RDG...THE MODELS BRING A FAST-MOVING WEAK CLIPPER SYSTEM INTO
THE UPR MS VALLEY. EXPECT TO SEE CLOUDS FROM THIS SYSTEM TO
ALREADY BE OVERSPREADING AT LEAST NRN WI LATE FRI NGT...BUT ANY
PCPN SHOULD REMAIN TO OUR WEST. THE INITIAL MOSTLY CLEAR TO PARTLY
CLOUDY SKIES WITH LIGHT WINDS WL ALLOW TEMPS TO FALL TO AROUND 20
DEGS FAR NORTH...MID TO UPR 20S SOUTH. THIS WEAK CLIPPER IS PROGGED
TO MOVE E-SE INTO THE GREAT LAKES ON SAT...ACCOMPANIED BY A CDFNT
AND A MID-LEVEL SHORTWAVE. MOISTURE AVAILABILITY LOOKS MARGINAL...
BUT THERE MAY BE ENUF LIFT/FORCING TO AT LEAST NEED THE MENTION OF
A SMALL POP ACROSS NE WI. A SLIGHT TUG OF WARMER AIR AHEAD OF THIS
CLIPPER SHOULD HELP BOOST MAX TEMPS INTO THE 40-45 DEG RANGE NORTH...
UPR 40S TO LWR 50S SOUTH.

FCST FOR THE LATTER HALF OF THE WEEKEND REMAINS UNCERTAIN...DEPENDING
ON HOW FAR THE CDFNT CAN SAG BEFORE PULLING UPR STNRY. ALL THE MODELS
DEVELOP A FRONTOGENETIC BAND OF LIGHT PCPN ALONG/JUST NORTH OF THIS
STNRY FNT...THUS THE FNT`S LOCATION IS KEY TO PCPN CHCS OVER NE WI
SAT NGT INTO SUNDAY. LATEST THINKING HAS THE FNT REACHING SRN WI
BEFORE STALLING...THUS THIS LEAVES CNTRL/E-CNTRL WI VULNERABLE TO THE
PCPN POTENTIAL DURING THE LATE SAT NGT/SUNDAY MORNING TIME FRAME
BEFORE THE FNT SLIPS FARTHER SOUTH INTO NRN IL SUNDAY AFTERNOON.
HAVE RAISED POPS FOR THE SRN HALF OF THE FCST AREA DURING THIS PERIOD
AND WITH TEMPS FALLING BELOW FREEZING SAT NGT/EARLY SUNDAY MORNING...
WE MAY HAVE A MINOR SNOW ACCUMULATION TO DEAL WITH. TOO MUCH
UNCERTAINTY YET ON HOW THIS WL PLAY OUT...THUS WL HOLD OFF ON ANY
POTENTIAL ACCUMULATION IN THE FCST/HWO.

FCST CONFIDENCE REMAINS LOW HEADED INTO THE NEW WORK WEEK WITH THE
MODELS CONTINUING TO SHOW DIFFERENT LOCATIONS FOR THE QUASI-STNRY
FNT. IF THE FNT REMAINS TO OUR SOUTH...MON COULD BE DRY WITH A DRY
EAST WIND FROM HI PRES OVER ONTARIO. HOWEVER...IF THIS FNT BEGINS
TO DRIFT NORTH A LITTLE ON MON...THIS WOULD INCREASE OUR PCPN CHCS.
FOR NOW...HAVE FOLLOWED THE CONSENSUS SOLUTION WHICH KEEPS CHC POPS
OVER THE ENTIRE FCST AREA FOR MON AND TUE. PCPN TYPE WL ALSO CONT
TO BE PROBLEMATIC AS TEMPS FALL BELOW FREEZING AT NGT AND RISE
INTO THE 40S DURING THE DAY. ONE POSITIVE FROM ALL OF THIS WOULD
BE ENUF PCPN FALLS TO ALLEVIATE THE DRY CONDITIONS OVER THE REGION.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 643 AM CDT WED APR 1 2015

ASIDE FROM SOME PATCHY LOW CLOUDS NEAR THE UPPER MICHIGAN BORDER...
MOST PLACES HAD SCT-BKN MID-LEVEL CLOUDS EARLY THIS MORNING.
RADAR SHOWED SOME LIGHT RETURNS OVER NORTHERN WI...BUT THESE WERE
NOT REACHING THE GROUND DUE TO A DEEP LAYER OF DRY AIR. A FEW
LIGHT SHOWERS MAY DEVELOP ACROSS NORTHERN WI TODAY...BUT THE MAIN
BRUNT OF THE SHOWER ACTIVITY...AND A FEW THUNDERSTORMS...WILL
ACCOMPANY A COLD FRONT AS IT MOVES THROUGH THE FORECAST AREA
TONIGHT AND EARLY THURSDAY. MVFR CONDITIONS WILL BE POSSIBLE WITH
THE STEADIER PRECIPITATION.

GUSTY SOUTH TO SOUTHEAST WINDS WILL DEVELOP BY MIDDAY TODAY...AND
BECOME WESTERLY AFTER THE FRONT PASSES.

WILL CARRY LLWS FOR ALL OF THE TAF SITES TONIGHT...AS SW WINDS INCREASE
TO 40 TO 50 KTS JUST ABOVE THE SURFACE. THE LLWS WILL DIMINISH AFTER
THE COLD FRONT MOVES THROUGH.
&&

.FIRE WEATHER...
ISSUED AT 415 AM CDT WED APR 1 2015

FIRE DANGER WILL BE ELEVATED OVER CENTRAL WI THIS AFTERNOON AS
TEMPS APPROACH 70 DEGREES...SOUTH WINDS GUST TO 25 TO 30 MPH AND
RELATIVE HUMIDITY DROPS TO AROUND 30 PERCENT.

ANOTHER PERIOD OF INCREASED FIRE DANGER IS POSSIBLE ON THURSDAY
AFTERNOON...AS A DRY SLOT BRINGS CLEARING SKIES AND GUSTY WEST
WINDS TO THE REGION...AND RELATIVE HUMIDITY DROPS INTO THE
20 TO 25 PERCENT RANGE IN THE SANDY SOIL REGIONS OF NC/C/NE WI.
THE BIG QUESTION WILL BE WHETHER OR NOT GRASSES AND OTHER FINE
FUELS CAN DRY OUT SUFFICIENTLY AFTER RECEIVING MODERATE RAINFALL
TONIGHT/EARLY THURSDAY.
&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......KALLAS
AVIATION.......KIECKBUSCH
FIRE WEATHER...KIECKBUSCH





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