Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 151123
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
623 AM CDT MON SEP 15 2014

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 326 AM CDT MON SEP 15 2014

SEVERAL FCST CONCERNS TO DEAL WITH OVER THE NEXT 36 HOURS. THE
PRIMARY CONCERN TO BE THE NRN EXTENT OF PCPN ACROSS THE FCST AREA
TODAY AS A COMPACT SHORTWAVE TROF SWINGS THRU THE REGION MAINLY
DURING THE MORNING HOURS. THE OTHER CONCERN WL BE TEMPS TNGT AS
SKIES CLEAR...WINDS GO LIGHT AND THE POTENTIAL FOR ANOTHER FROSTY
NGT ACROSS THE NORTH.

THE 07Z MSAS SFC ANALYSIS INDICATED A CDFNT EXTENDED FROM ERN
ONTARIO SWWD THRU SW WI TO CNTRL KS. HI PRES WAS LOCATED OVER THE
NRN PLAINS AND THE ERN GREAT LAKES. RADAR MOSAIC SHOWED A LARGE
BAND OF LIGHT SHOWERS STRETCHED FROM ERN SD EWD THRU CNTRL WI INTO
NRN LWR MI.

WHILE THE CDFNT WL CONT TO DROP SE THRU THE REST OF WI THIS
MORNING...THE MAIN WEATHER FEATURE OF INTEREST TO BE A SHORTWAVE
TROF/STRENGTHENING EMBEDDED SHORTWAVE THAT ALL THE MDLS QUICKLY
MOVE INTO THE WRN GREAT LAKES THIS MORNING. THIS IS A DYNAMIC
QUICK-HITTING SYSTEM WITH FAVORABLE Q-G/FRONTOGENETICAL FORCING
AND A PSEUDO-COUPLED JET STRUCTURE. EXPECT TO SEE THE CURRENT BAND
OF LIGHT SHOWERS OVER WI TO INCREASE IN BOTH COVERAGE AND
INTENSITY OVER THE SRN HALF OF WI WITH QPF AMOUNTS AROUND 0.25"
POSSIBLE OVER SRN SECTIONS OF THE FCST AREA (Y50-MTW LINE). PCPN
CHCS TAIL OFF OVER NRN WI WHERE ONLY A SPOTTY SHWR OR SPRINKLES
ARE POSSIBLE DUE TO MORE OF A DAYTIME HEATING/COOL AIR ALOFT
SITUATION. THIS SHORTWAVE TROF TO ALREADY BY PULLING AWAY FROM WI
THIS AFTERNOON WITH STRONG SUBSIDENCE AND DRIER AIR ADVECTING EWD
FROM THE HI PRES OVER THE CNTRL PLAINS/UPR MS VALLEY. LOOK FOR
DECREASING CLOUDS LATER THIS AFTERNOON WITH MAX TEMPS GENERALLY
AROUND THE 60 DEG MARK.

THE CENTER OF THE HI PRES TO MOVE INTO THE MIDWEST TNGT...PLACING
NE WI IN ITS NRN FRINGES WITH BOUNDARY LAYER WINDS IN THE 10 TO 20
MPH RANGE. SKIES SHOULD BE MOSTLY CLEAR WITH LIGHT SFC WINDS WHICH
BRINGS FROST INTO THE PICTURE WITH THE COOL AIR MASS OVERHEAD. NRN
WI TO BE THE COLDEST TNGT...BUT ALSO HAS THE STRONGEST OF THE
BOUNDARY LAYER WINDS...THUS CAN ENUF FROST TO DEVELOP TO WARRANT
AN ADVY? AFTER COLLABORATION WITH DLH AND MQT...HAVE DECIDED TO GO
AHEAD AND ISSUE A FROST ADVY TNGT FOR NRN WI. PATCHY FROST/FOG MAY
STILL DEVELOP OVER PARTS OF CNTRL/E-CNTRL WI LATE TNGT...BUT NOT
BE WIDESPREAD ENUF TO INCLUDE IN THE ADVY.

THE SFC HI CONTS TO DRIFT EAST TOWARD SRN SECTIONS OF THE GREAT
LAKES ON TUE AND SHOULD KEEP MOSTLY SUNNY SKIES INTACT THRU THE
DAY. THERE MAY BE AN INCREASE IN HI CLOUDS OVER NRN WI LATER TUE
AFTERNOON AS A CDFNT DROPS SOUTH INTO LAKE SUPERIOR. MAX TEMPS ON
TUE WL BE WARMER DUE TO THE PLENTIFUL SUNSHINE AS READINGS REACH
THE LWR TO MID 60S NORTH/LAKESHORE...MID TO UPR 60S ELSEWHERE.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 326 AM CDT MON SEP 15 2014

TIMING THE CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BE THE MAIN
CONCERN DURING THIS PART OF THE FORECAST.

A CHANGE IN THE UPPER LEVEL PATTERN ACROSS THE CONUS CAN BE
EXPECTED BY LATE IN THE WEEK. THE TROUGH IN THE EAST AND RIDGE IN
THE WEST GRADUALLY BREAK DOWN AND FLOW BECOMES MORE ZONAL LATE IN
THE WEEK. MODELS SHOW DIFFERENCES IN TIMING OF SYSTEMS IN THE
QUICKER ZONAL FLOW SO ONSET OF PRECIPITATION AND ITS ENDING TIME
REMAIN SOMEWHAT IN QUESTION. THE STRENGTH OF AN UPPER LEVEL TROUGH
AND APPROACHING SURFACE LOW PRESSURE SYSTEM...THAT ARE FORECAST TO
IMPACT THE REGION LATER IN THE WEEKEND...IS ALSO UNCERTAIN AT
THIS TIME.

FOR THE EARLY PART OF THE FORECAST SURFACE HIGH PRESSURE LOOKS TO
BE THE MAIN FEATURE ACROSS THE REGION. THIS SHOULD RESULT IN DRIER
CONDITIONS. A BACKDOOR COLD FRONT COULD BRING SOME SHOWERS TO THE
FAR NORTHERN PART OF THE STATE SO HAVE SOME SLIGHT CHANCE POPS
WEDNESDAY INTO WEDNESDAY NIGHT. SOME MODELS INDICATED QPF IN THE
AREA SO POPS MAY NEED TO BE INCREASED IN LATER FORECASTS.

HAVE ADDED PRECIPITATION CHANCES EARLIER IN THE FORECAST THAN ON
MY PREVIOUS SHIFT AS SYSTEMS LOOK TO BE MOVING FASTER. HAVE A
SLIGHT CHANCE FOR SHOWERS ON THURSDAY NIGHT...WITH POPS INCREASING
TO THE CHANCE CATEGORY ON FRIDAY. BUFKIT TIME/HEIGHT SECTIONS
SHOWED SOME ELEVATED INSTABILITY ON FRIDAY SO HAVE ALSO MENTIONED
A SLIGHT CHANCE FOR THUNDER. ELEVATED CAPE VALUES ARE HIGHER ON
FRIDAY NIGHT SO HAVE ONLY MENTIONED THUNDER...WITH CHANCE POPS IN
THE EAST AND LIKELY POPS IN THE NORTHWEST. HAVE POPS DECREASING TO
CHANCE ON SATURDAY AND SLIGHT CHANCE ON SUNDAY.

BELOW NORMAL HIGH TEMPERATURES CAN BE EXPECTED FOR MOST OF THE
WEEK...BUT THEY SHOULD WARM UP SATURDAY AHEAD OF AN APPROACHING
COLD FRONT.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 622 AM CDT MON SEP 15 2014

A FAST-MOVING SHORTWAVE TROF IS FCST TO SWEEP ACROSS THE WRN GREAT
LAKES REGION THIS MORNING. AN EXPANSIVE BAND OF LIGHT RAIN SHWRS
WILL MOVE ACROSS THE SRN HALF OF WI DURING THE MORNING HOURS AND
THEN DIMINISH FROM WEST TO EAST IN THE AFTERNOON. WHILE MAINLY VFR
CONDITIONS ARE EXPECTED THIS MORNING...THERE COULD BE A BRIEF
PERIOD OF MVFR VSBYS ASSOCIATED WITH A HEAVIER SHWR. HI PRES IS
THEN FCST TO BEGIN BUILDING EWD FROM THE PLAINS THIS AFTERNOON
AND BRING CLEARING SKIES TO NE WI. VFR CONDITIONS WL PREVAIL TNGT
AND ON TUE AS THE HI PRES PASSES BY JUST TO OUR SOUTH.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM CDT TUESDAY FOR
WIZ005-010>013-018-019-021.
&&

$$

SHORT TERM.....AK
LONG TERM......MG
AVIATION.......AK





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