Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 300441
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1141 PM CDT WED JUL 29 2015

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 252 PM CDT WED JUL 29 2015

AN UNUSUALLY STRONG LOW PRESSURE SYSTEM FOR LATE JULY WAS PASSING
ACROSS ONTARIO THIS AFTERNOON. TEMPERATURES THIS AFTERNOON WERE
IN THE MIDDLE AND UPPER 70S ACROSS THE FAR NORTH...AND LOWER TO
MIDDLE 80S OVER THE REMAINDER OF THE REGION. TIGHT PRESSURE
GRADIENT AND DEEP MIXING HAS CAUSED WIND GUSTS OF 30 TO 40 MPH
AT MOST LOCATIONS. WAUSAU DID TAP THE EVEN HIGHER WINDS ALOFT...
WITH A WIND GUST TO 46 MPH DURING THE PAST HOUR.

THE GUSTY WEST WINDS WILL QUICKLY SUBSIDE AROUND SUNSET WITH
WESTERLY WINDS OF 5 TO 10 MPH EXPECTED AT MOST PLACES FROM LATE
EVENING AND OVERNIGHT. WINDS MAY BE A TAD BIT STRONGER OVER NORTHERN
DOOR COUNTY. WARMEST LOW TEMPERATURES ARE EXPECTED TO BE ACROSS
NORTHERN DOOR COUNTY WHERE WEST WIND WILL MOVE OVER THE WARMER
WATERS OF THE BAY OF GREEN BAY.

ON THURSDAY...AN UPPER LEVEL DISTURBANCE WILL MOVE ACROSS NORTHERN
WISCONSIN. SOME TIMING DIFFERENCES NOTED ON THE MODELS. HAVE ADDED
A SMALL CHANCE OF THUNDERSTORMS ACROSS FAR NORTH-CENTRAL WISCONSIN
FOR THIS FEATURE. MODIFIED SOUNDING INDICATED HIGH BASE CONVECTION
AROUND 8000 FEET. THIS SCENARIO IS MORE TYPICALLY SEEN OUT IN THE
WESTERN UNITED STATES. IF ANY STORMS DO DEVELOP...THEY WILL BE
CAPABLE OF PRODUCING STRONG GUSTY WINDS. HIGH TEMPERATURES SHOULD
AGAIN WARM INTO THE UPPER 70S TO MIDDLE 80S...EVEN ON THE LAKESHORE.
GUSTY WEST WINDS ARE EXPECTED AGAIN THURSDAY AFTERNOON...BUT NOT
AS STRONG AS TODAY.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 252 PM CDT WED JUL 29 2015

UPPER LOW WILL REMAIN ANCHORED NEAR HUDSON BAY CANADA THROUGH
EARLY NEXT WEEK. MEANWHILE UPSTREAM...BROAD LOW AMPLITUDE RIDGING
OVER THE NORTHERN ROCKIES WILL BECOME SOMEWHAT MORE AMPLIFIED BY
EARLY NEXT WEEK. THIS WILL LEAVE THE WESTERN GREAT LAKES WITHIN A
NORTHWESTERLY UPPER-LEVEL FLOW THROUGH THE FORECAST PERIOD.
TEMPERATURES WILL REMAIN AT OR A FEW DEGREES ABOVE NORMAL THROUGH
THE UPCOMING WEEKEND...THEN TREND TOWARD SLIGHTLY BELOW NORMAL
EARLY NEXT WEEK AS THE UPPER-LEVEL FLOW BECOMES A BIT MORE
AMPLIFIED. THE FORECAST CHALLENGE WILL REVOLVE AROUND TIMING AND
INTENSITY OF WEAK SHORTWAVE DISTUBANCES GREAT LAKES EMBEDDED
WITHIN THIS FLOW AS THEY IMPINGE ON THE WESTERN GREAT LAKES.

THURSDAY NIGHT THROUGH FRIDAY...CONCENSUS OF MODEL GUIDANCE
SUGGESTS SEVERAL FAST MOVING WEAK IMPULSES WILL MOVE EAST-
SOUTHEAST ACROSS NORTHERN WISCONSIN OR UPPER MICHIGAN. THESE
DISTURBANCES WILL HAVE LITTLE MOISTURE AND ONLY WEAK SURFACE
TROUGHINESS ASSOCIATED WITH THEM. THE ONLY DISTURBANCE THAT MAY
HAVE A CHANCE OF GENERATING SOME VERY LIGHT SHOWER ACTIVITY WOULD
BE THE ONE TO AFFECT THE AREA FRIDAY. BEST GUESS IS THAT THE
TIMING OF THIS FEATURE WOULD BE SOMETIME FRIDAY AFTERNOON AS THE
WEAK SURFCACE TROUGH MOVES THROUGH. AS PER PREVIOUS FORECAST WILL
KEEP VERY LOW CHANCE POPS CONFINED TO THE FAR NORTH FOR FRIDAY
AFTERNOON.

FORECAST BECOMES MORE UNCERTAIN SATURDAY NIGHT AND SUNDAY AS
A COUPLE SOMEWHAT MORE SUBSTANTIAL DISTURBANCES APPROACH THE
REGION. ECMWF SUGGESTS MORE PRONONCED IMPULSE OVER THE CENTRAL
PLAINS GENERATING A CONVECTIVE COMPLEX OVER IOWA LATE SUNDAY NIGHT
WHICH GENERALLY STAYS SOUTHWEST OF THE AREA. MEANWHILE THE GFS
SUGGESTS MORE CONVECTIVE ACTIVITY OVER MINNESOTA AND WISCONSIN BY
SUNDAY MORNING ASSOCIATED WITH A MORE PRONOUNCED NORTHERN UPPER-
LEVEL IMPULSE. REGARDLESS...BOTH SCENARIOS INDICATE MORE
PRONOUNCED LOW-LEVEL WAA AND SOMEWHAT DEEPER MOISTURE AHEAD OF AN
APPROACHING FRONTAL BOUNDARY. THUS MAINTAINED CHANCE POPS OVER
MOST OF THE FORECAST AREA SATURDAY NIGHT INTO SUNDAY MORNING.
GUIDANCE ALSO SUGGESTS YET ANOTHER IMPULSE TO FOLLOW ON THE HEELS
OF THE FIRST WHICH COULD IMPACT THE AREA SUNDAY NIGHT INTO MONDAY
IN THE VICINITY OF A FRONTAL BOUNDARY DRAPED SOMEWHERE ACROSS
CENRAL WISCONSIN BY 06Z MONDAY. THUS WILL MAINTAIN CHANCE POPS
SUNDAY NIGHT INTO TUESDAY WITH DETAILS TO BE WORKED OUT IN LATER
FORECASTS. TEMPERATURES FOR SUNDAY AND MONDAY WILL BE AT THE WHIM
OF THE TIMING OF THESE DISTURBANCE AND THEIR ASSOCIATED CLOUDS
AND PRECIPITATION...THUS LEANED ON THE MODEL BLEND.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1133 PM CDT WED JUL 29 2015

CYCLONIC FLOW IS EXPECTED TO PERSIST ACROSS THE AREA THROUGH
THURSDAY NIGHT...BUT VFR CONDITIONS SHOULD PREVAIL. AN UPPER LEVEL
SHORT WAVE WAS FORECAST TO PASS THROUGH WISCONSIN DURING THE DAY
ON THURSDAY WITH SOME OF THE MODELS PRODUCING RAIN AND OTHERS NOT.
THE 00Z GFS/00Z CANADIAN WERE DRY...THE 00Z NAM ONLY SPIT OUT A
SMALL AREA OF LIGHT QPF...WHILE THE 12Z ECMWF AND 21Z SREF HAD
MORE WIDESPREAD AND HIGHER QPF. ANOTHER SHORT WAVE APPROACHES
WISCONSIN THURSDAY EVENING BUT MODELS WERE NOT IN AGREEMENT WITH
THAT SYSTEM EITHER. AS A RESULT...THE FORECAST REMAINS DRY WITH
ONLY SOME SCATTERED TO BROKEN VFR CIGS. WINDS WILL INCREASE AGAIN
DURING THE DAY BUT GUSTS WILL NOT BE NEARLY AS HIGH AS THEY WERE
DURING THE DAY ON WEDNESDAY.
&&

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

$$

SHORT TERM.....ECKBERG
LONG TERM......ESB
AVIATION.......MG



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