Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 020021
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
721 PM CDT TUE SEP 1 2015

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 224 PM CDT TUE SEP 1 2015

MAIN FCST CONCERNS FOR TNGT WL BE THE SMALL THREAT OF SHWRS/TSTMS
NORTH THIS EVENING AND FOG DEVELOPMENT TNGT. CONCERNS TURN TO
EXTENT OF PCPN ON WED AS A MID-LEVEL SHORTWAVE INTERACTS WITH AN
UNSTABLE AND JUICY AIR MASS OVER WI.

THE 19Z MSAS SFC ANALYSIS INDICATED A WEAK AREA OF HI PRES OVER
WI...A WEAK CDFNT THAT EXTENDED FROM WRN LAKE SUPERIOR SW TO SW MN
AND A SUMMERLIKE AIR MASS OVERHEAD WITH DEW POINTS IN THE MID 60S
TO MID 70S.

THE WEAKENING CDFNT IS FCST TO ESSENTIALLY WASHOUT OVER NRN WI
TNGT...SO THE THREAT OF PCPN FROM THIS SYSTEM PRETTY MUCH IS
LIMITED TO SLGT CHC ACROSS THE NORTH EARLY THIS EVENING. ANOTHER
FEATURE TO WATCH WL BE A MID-LEVEL SHORTWAVE TROF THAT IS EXPECTED
TO MOVE NEWD INTO THE MIDWEST LATE TNGT. MODELS INDICATE AN AREA
OF SHWRS/TSTMS TO DEVELOP AHEAD OF THIS TROF...THUS A SMALL CHC
FOR CNTRL WI STILL LOOKS PRUDENT. THE REST OF NE WI SHOULD REMAIN
DRY...WARM AND MUGGY TNGT WITH AREAS OF FOG DEVELOPING AGAIN DUE
TO LIGHT WINDS AND ABUNDANT LOW-LEVEL MOISTURE. MIN TEMPS TO RANGE
FROM THE LWR TO MID 60S NORTH...MID TO UPR 60S SOUTH.

THIS SHORTWAVE TROF (WITH ITS EMBEDDED SHORTWAVE) CONTS TO TRACK
NE AND CUTS THRU THE CENTER OF WI ON WED. INCREASING MID-LEVEL
FORCING...COOLER AIR ALOFT AND STEEPER MID-LEVEL LAPSE RATES
SHOULD ALLOW FOR SHWRS/TSTMS TO MOVE INTO THE FCST AREA. HAVE
RAISED POPS A BIT FROM THE PREVIOUS FCST AND WL HAVE TO KEEP AN
EYE ON THE STORMS AS INSTABILITY IS MODERATELY STRONG (CLOSE TO
2K J/KG). SHEAR IS RATHER WEAK (< 20 KTS)...THUS EXPECT PULSE-TYPE
TSTMS WITH A POTENTIAL FOR SUB-SEVERE HAIL AND BRIEF GUSTY WINDS.
FOR AREAS THAT STAY PCPN-FREE...ANOTHER VERY WARM AND HUMID DAY IS
FCST WITH MAX TEMPS IN THE LWR 80S NEAR LAKE MI/N-CNTRL WI...
MAINLY MID 80S EVERYWHERE ELSE.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 224 PM CDT TUE SEP 1 2015

PCPN CHANCES WEDS NGT/THU...AND A COLD FRONTAL PASSAGE AND
SUBSEQUENT COOL DOWN EARLY NEXT WEEK...ARE THE MAIN FCST CONCERNS.

A S/W TROF IS EXPECTED MOVE THROUGH THE FCST AREA WEDS NGT AND
EARLY THURSDAY. MODELS HAVE INCREASED QPF AMOUNTS...ESPECIALLY
OVER C/EC WI...SO WILL RAISE POPS TO 40-50 PERCENT THERE. WOULD
CONSIDER LIKELY POPS GIVEN HIGH PRECIPITABLE WATER VALUES (1.50
TO 2 INCHES)...BUT THIS SYSTEM IS NOT CURRENTLY PRODUCING MUCH
CONVECTION IN THE NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY...
SO WILL SEE HOW THIS EVOLVES. PCPN CHANCES SHOULD TAPER OFF FROM
NW TO SE ON LATE WEDS NGT INTO THURSDAY AS THE S/W TROF SAGS SE.

THE UPPER RIDGE IS EXPECTED TO BUILD AGAIN THURSDAY NIGHT THRU
SAT NIGHT...WITH 500 MB HEIGHTS RISING TO 590 EARLY THIS
WEEKEND. EXPECT LITTLE RAIN DURING THIS PERIOD...WITH CONTINUED
VERY WARM AND HUMID CONDITIONS.

A COLD FRONTAL PASSAGE IS EXPECTED TO OCCUR SUNDAY NIGHT INTO
MONDAY...AND THIS SHOULD PROVIDE THE NEXT SIGNIFICANT CHANCE OF
RAIN. MUCH COOLER AND LESS HUMID CONDITIONS ARE EXPECTED TO ARRIVE
IN THE WAKE OF THIS FRONT...WITH HIGH TEMPS DROPPING INTO THE
UPPER 60S TO MIDDLE 70S BY TUESDAY.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 720 PM CDT TUE SEP 1 2015

ATMOSPHERE REMAINS MOIST WITH DEW POINTS IN THE UPR 60S TO LOW 70S
AND WINDS BECOMING LIGHT ONCE AGAIN OVERNIGHT. THUS EXPECT
ANOTHER ROUND OF FOG TO DEVELOP OVER MUCH OF THE FORECAST AREA
LATE TONIGHT...WITH IFR/MVFR VSBYS PERSISTING TIL 14Z.

MID-LEVEL SHORTWAVE TROF OVER THE CNTRL PLAINS IS FCST TO MOVE NE
TOWARD WISCONSIN OVERNIGHT. THIS SYSTEM IS SLOW MOVING AND IS
FCST TO BRING ISOLATED TO SCT SHWRS AND TSTMS TO WESTERN WISCONSIN
STARTING LATE TNGT. AS THE SHORTWAVE DISTURBANCE INTERACTS WITH
MORE INSTABILITY DURING THE DAY ON WEDNESDAY...EXPECT SOMEWHAT
MORE WIDESPREAD SHOWER AND TSTM ACTIVITY ACCOMPANIED BY MVFR
CIGS/VSBYS.

THE VERY MOIST AND MODERATELY UNSTABLE ATMOSPHERE...IN CONCERT
WITH RELATIVELY LIGHT WINDS ALOFT...WOULD FAVOR SLOW MOVING AND
MORE DISORGANIZED SUB-SEVERE PULSE-TYPE STORMS CAPABLE OF
PRODUCING LOCALLY HEAVY DOWNPOURS.
&&

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

$$

SHORT TERM.....KALLAS
LONG TERM......KIECKBUSCH
AVIATION.......ESB



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