Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 202227
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
527 PM CDT SUN APR 20 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 330 PM CDT SUN APR 20 2014

TRYING TO DECIPHER TIMING OF PCPN BANDS TNGT AND MON CONT TO BE
THE BIGGEST FCST ISSUE TO DEAL WITH. TEMPS AND THUNDER THREAT ALSO
HAVE TO BE ADDRESSED.

THE 19Z MSAS SFC ANALYSIS SHOWED A STALLED FRONTAL BOUNDARY
EXTENDED FROM S-CNTRL MN NE THRU N-CNTRL WI INTO CNTRL LAKE
SUPERIOR. ONE SFC LOW WAS LOCATED OVER NE NEBRASKA...WHILE TWO
OTHER SFC LOWS WERE SITUATED OVER THE NRN PLAINS. VSBL SATL
IMAGERY INDICATED A BAND OF LOW/MID CLOUDS STRETCHED FROM NE IA
NEWD INTO SE ONTARIO. RADAR MOSAIC HAD PICKED UP A BAND OF SHWRS
LOCATED SOUTH OF THE STALLED BOUNDARY.

FOCUS FOR ADDITIONAL SHWRS (PSBL TSTM) ACTIVITY TO BE ALONG THIS
STALLED BOUNDARY DRAPED ACROSS CNTRL WI TNGT. OVERALL FORCING AND
LIFT REMAIN MARGINAL...BUT PCPN IS EXPECTED TO PERSIST ALONG THE
BOUNDARY WHERE WEAK CONVERGENCE TO BE MAXIMIZED. FORCING DOES
INCREASE A BIT LATER TNGT AS A WEAK SRN STREAM SHORTWAVE TROF
LIFTS NE INTO THE MIDWEST/MID-MS VALLEY. N-CNTRL WI COULD VERY
WELL STAY DRY TNGT...BUT THIS LEADS TO FOG POTENTIAL DUE TO
MOISTURE FROM MELTING SNOW...LIGHT WINDS AND DEW POINTS REMAINING
ABOVE FREEZING. QUITE A CONTRAST IN TEMPS EXPECTED TNGT WITH THE
NORTHWOODS FALLING INTO THE MID 30S...WHILE SRN SECTIONS OF THE
FCST AREA MAY NOT FALL BELOW 50 DEGS.

SHWR/ISOLATED TSTM ACTIVITY TO CONT THRU AT LEAST MON MORNING OVER
THE ENTIRE FCST AREA AS THE SRN STREAM SHORTWAVE TROF SHIFTS
TOWARD THE ERN GREAT LAKES AND A NRN STREAM SHORTWAVE TROF MOVES
INTO NRN SECTIONS OF THE GREAT LAKES. AT THE SFC...A CDFNT IS
PROGGED TO MOVE ACROSS WI...DISPLACE THE STALLED BOUNDARY AND ACT
AS A FOCUS FOR THE PCPN. BY MON AFTERNOON...THE SHWRS ARE EXPECTED
TO DIMINISH OVER N-CNTRL WI/PARTS OF CNTRL WI BEHIND THE CDFNT.
INSTABILITY STILL LOOKS MARGINAL ON MON WITH CAPES PUSHING 500
J/KG OVER CNTRL/E-CNTRL WI...THUS HAVE MAINTAINED THE ISOLATED
THUNDER WORDING IN THE FCST. MILD START TO THE DAY WL STILL ALLOW
TEMPS TO WARM INTO THE 60S (50S LAKESIDE) EVEN AS WINDS TURN NW
AND WEAK CAA STARTS.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 330 PM CDT SUN APR 20 2014

HIGHLIGHTS FOR THE LONG TERM PORTION...AFTER A FEW LINGERING
SHOWERS MONDAY EVENING WITH A DEPARTING FRONTAL SYSTEM...DRIER
CONDITIONS EXPECTED MONDAY NIGHT INTO MOST OF WEDNESDAY. FORECAST
CONCERN THEN TURNS TO MID WEEK WITH A DEEPENING UPPER SYSTEM
FORECAST TO TRACK ACROSS THE MID SECTION OF THE COUNTRY. AFTER
THIS SYSTEM...PCPN TYPE ISSUES INCREASE FOR LATE NEXT WEEKEND.

DRY HIGH PRESSURE RIDGE TO DRIFT OVER THE REGION MONDAY NIGHT
INTO TUESDAY NIGHT BEFORE DRIFTING EAST ON WEDNESDAY. COOL NIGHT
IN STORE TUESDAY NIGHT WITH LIGHT WINDS UNDER THE RIDGE AXIS.

PROGS CONTINUE TO LIFT A WARM FRONT NORTH LATER WEDNESDAY INTO
WEDNESDAY NIGHT. INITIAL WAA AND RETURN MOISTURE WILL BE
ENCOUNTERING SOME COOL DRY AIR OVER THE FAR NORTHEAST FOR A
POSSIBLE MIX EARLY WEDNESDAY NIGHT...BUT POTENTIAL TOO SMALL AT THIS
TIME TO ADD TO THE FORECAST. HAVE TO KEEP ANY EYE OUT FOR THESE
UPPER SYSTEMS DUE TO HAIL POTENTIAL FROM LOW WET BULB PARAMETERS.
WHILE LI/S APPEAR MINIMAL AT THIS TIME...GFS TOTAL TOTALS NEAR THE
MID 50S THURSDAY AFTERNOON WITH THE PASSAGE OF A COLD OR OCCLUDED
FRONT. LATEST ECMWF CONFINES BEST INSTABILITY SOUTH OF THE AREA.

MUCH COOLER TEMPERATURES ARRIVE FOR NEXT WEEKEND. EACH THE GFS
AND ECMWF HAVE SLOWED DOWN THE ARRIVAL OF THE PCPN FOR LATE NEXT
WEEKEND. A H850 WARM FRONT IS PROGGED TO LIFT INTO NORTHERN
ILLINOIS SUNDAY AFTERNOON INTO SUNDAY NIGHT...WITH RETURN FLOW
PCPN SPREADING NORTHWARD INTO THE STATE. THIS RETURN FLOW WILL BE
WORKING NORTHWARD INTO A COOLER AND DRIER AIR MASS WHICH COULD
PRODUCE PCPN TYPE ISSUES LATE NEXT WEEKEND.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 523 PM CDT SUN APR 20 2014

BAND OF MOISTURE/CLDS/PCPN AHEAD OF COLD FRONT SAGGING INTO THE
AREA FM THE NW WL CONT ACRS SW-EC WI THIS EVENING. RADAR SUGGESTS
A LULL WL OCCUR EARLY IN THE EVENING...WITH REDEVELOPMENT LATER IN
THE EVENING/OVERNIGHT. GENERALLY VFR CONDITIONS WERE ACRS THE
AREA...WITH PATCHES OF LOWER CIGS/VSBYS WITH THE PCPN. COULD SEE
SOME MORE WIDESPREAD LOWER CONDITIONS DEVELOP ACRS THE N LATE TNGT
UNDER CLR SKIES AND LGT WINDS...BUT IT WL TAKE QUITE A WHILE FOR
TEMPS TO FALL TO TD/S AS MIXING INTO DRIER AIR ALOFT OCCURRED THIS
AFTN AND RH/S WERE NOW QUITE LOW.

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

$$

SHORT TERM.....AK
LONG TERM......TDH
AVIATION.......SKOWRONSKI






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