Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 220357
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1057 PM CDT THU AUG 21 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.UPDATE...
ISSUED AT 835 PM CDT THU AUG 21 2014

HAVE INCREASED POPS ACROSS NORTH CENTRAL AND FAR NE WI THIS EVG
AND EARLY FRIDAY MORNING TO ACCOUNT FOR UPSTREAM CONVECTION
APPROACHING FROM NW WI. THIS CONVECTION IS BEING DRIVEN BY A S/W
TROF AND H8 WAA/ISENT LIFT. ALTHOUGH INSTABILITY IS CURRENTLY
QUITE WEAK OVER THE ENTIRE CWA...INCLUDING NORTHERN WI...ELEVATED
INSTABILITY IS EXPECTED TO INCREASE LATER THIS EVG AND OVERNIGHT.
JUST KEPT LOW END 20-30 POPS FOR THE REST OF THE CWA...BUT WILL
NEED TO WATCH TRENDS OVER THE NEXT FEW HOURS.

HAVE ALREADY RECEIVED A REPORT OF DENSE FOG EAST OF WAUSAU...SO
THERE IS SOME CONCERN ABOUT FOG TRENDS FOR THE REST OF THE NIGHT.
CONTINUED LIGHT EAST FLOW AND ABUNDANT MOISTURE IN THE LOW-LEVELS
IS FAVORABLE FOR FOG DEVELOPMENT...ESPECIALLY IN THE HIGHER TERRAIN
OF NC WI AND ALONG THE LAKESHORE. HOWEVER...CONFIDENCE IS NOT HIGH
ENOUGH TO ISSUE A DENSE FOG ADVISORY AT THIS TIME. WILL PROBABLY
UPDATE THE HWO AND ISSUE AN SPS TO HANDLE THE SITUATION FOR NOW.
&&

.SHORT TERM...TONIGHT AND FRIDAY
ISSUED AT 235 PM CDT THU AUG 21 2014

IN THE NEAR-TERM...FIRST BATCH OF RAIN ASSOCIATED WITH DECAYING
CONVECTIVE SYSTEM MOVED OUT OF FORECAST AREA DURING THE EARLY
AFTERNOON. CONSIDERABLE CLOUDS BEHIND SYSTEM INHIBITING ATMOSPHERE
FROM DESTABILIZING. ANY ADDITIONAL CONVECTION WILL BE TIED TO
UPPER LEVEL SHORTWAVE TROF THAT TOPS THE RIDGE AS IT MOVES ACROSS
MN INTO N WI TONIGHT. WHILE ADDITIONAL DEVELOPMENT CANNOT BE RULED
OUT ASSOCIATED WITH SURFACE FRONT THAT IS SUPPRESSED A BIT TO THE
SOUTH OF THE FORECAST AREA...THINK BETTER CHANCE FOR DEVELOPMENT MAY
BE IN THE NW HALF OF THE AREA...WHICH WOULD THEN SLIDE EAST OVERNIGHT.

FORCING THEN WANES LATER TNGT AS THE SHORTWAVE TROF SHIFTS E AND 850
MB FLOW VEERS WLY. UPR HEIGHTS ACRS THE AREA BUILD FRIDAY AND
UPPER FLOW BECOMES INCREASINGLY ANTICYCLONIC. HARD TO ABSOLUTELY
RULE OUT PRECIP GIVEN THE AVAILABLE MOISTURE AND POSSIBLE
BOUNDARIES ACRS THE REGION...THOUGH LARGE SCALE FORCING IS
DEFINITELY UNFAVORABLE. WILL KEEP VERY SMALL CHANCE/ISOLATED POPS.

TEMP FORECAST IS A BLEND OF PREVIOUS FORECAST AND BEST PERFORMING
SHORT-TERM GUIDANCE.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY
ISSUED AT 235 PM CDT THU AUG 21 2014

FRIDAY NIGHT INTO SATURDAY...PROGS IN GOOD AGREEMENT WITH THE
UPPER RIDGE BUILDING OVER THE WESTERN GREAT LAKES REGION. MODELS
ARE PRODUCING SPOTTY QPF IN THE WARM AND MOIST AIR MASS BUT WILL
CONTINUE WITH LOW END CHC POPS OR NO MEASURABLE POPS FOR THIS
STRETCH. MAIN FRONTAL SYSTEM WITH DEEP MOISTURE SAGS SOUTH OF THE
AREA STARTING FRIDAY NIGHT.

THE UPPER RIDGE IS PROGGED TO NUDGE EAST A LITTLE SATURDAY AS A
CLOSED LOW OR DEEP UPPER TROUGH DRIFTS INTO THE NORTHERN AND
CENTRAL PLAINS. H850 LLJ AHEAD OF THIS NEXT SYSTEM STARTS TO LIFT
A DEEP MOISTURE AND A MORE UNSTABLE AIR MASS OVER MINNESOTA AND
FAR WESTERN WISCONSIN LATER SATURDAY AND ESPECIALLY SATURDAY NIGHT
INTO SUNDAY. POPS WILL TEND TO BE HIGHER TO THE WEST SATURDAY AND
SATURDAY NIGHT AND EVEN PERHAPS SUNDAY...WITH THE UPPER RIDGE
PROTECTING EASTERN AREAS.

UPPER SYSTEM TRACKING OVER SOUTHERN CANADA SUNDAY NIGHT INTO
MONDAY NIGHT WILL DRAG A COLD FRONT OVER THE AREA. WHILE TIMING
ISSUES REMAIN WITH THIS FROPA PASSAGE...THE SLOW PROGRESSION
SUPPORTS A PCPN MENTIONED FOR SEVERAL PERIODS THROUGH MONDAY.

DEEPER AND MORE UNSTABLE AIR MASS GETS SHOVED SOUTH MONDAY NIGHT
INTO TUESDAY FOR ANOTHER PERIOD OF LOW END POPS. BUT PRECIP
CHANCES WILL RETURN NEXT WEEK WITH A SERIES OF COLD FRONT
PASSAGES ASSOCIATED WITH THE UPPER TROUGH SYSTEM OVER SOUTHERN
CANADA AND THE NORTHERN GREAT LAKES REGION. A DEVELOPING
BAROCLINIC ZONE MAY INTERACT WITH THE UPPER JET DYNAMICS FOR A FEW
PERIODS OF RAIN MID WEEK.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1051 PM CDT THU AUG 21 2014

WIDESPREAD IFR/LIFR CIGS COVERED MOST OF THE FCST AREA LATE THIS
EVG...AND PATCHY FOG WAS REPORTED ACROSS THE REGION. SCT SHRA/TSRA
WERE HEADED TOWARD PARTS OF C/NC WI. HAVE ADDED A TEMPO GROUP FOR
TSTMS TO THE AUW/CWA TAFS FROM 06Z/FRI-09Z/FRI...BUT BACKED OFF TO
JUST SHOWERS FOR THE RHI TAF.

EXPECT LOW CLOUDS AND FOG TO BE PREVALENT AT THE TAF SITES LATE
TONIGHT INTO FRIDAY MORNING...WITH IFR/LIFR CONDITIONS EXPECTED. A
GRADUAL IMPROVEMENT IN CIGS/VSBYS WILL OCCUR FRIDAY MORNING...BUT
MVFR CONDITIONS WILL LIKELY LINGER THROUGH THE AFTERNOON AND
EARLY EVENING. LOWER CIGS AND FOG WILL LIKELY RETURN BY MID TO
LATE FRIDAY EVENING.
&&

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

$$

UPDATE.........KIECKBUSCH
SHORT TERM.....JKL
LONG TERM......TDH
AVIATION.......KIECKBUSCH





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