649
FXUS63 KGRB 230932
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
432 AM CDT WED APR 23 2025
FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE
KEY MESSAGES
- THERE IS A CHANCE OF THUNDERSTORMS THIS AFTERNOON AND EVENING. A
FEW STRONG TO MARGINALLY SEVERE STORMS WITH HAIL ARE POSSIBLE
OVER THE FOX VALLEY AND LAKESHORE AREAS BETWEEN 2 PM AND 7 PM.
- PERIODIC PRECIPITATION CHANCES CONTINUE THROUGH FRIDAY, WITH THE
BEST CHANCE OF WIDESPREAD SIGNIFICANT RAINFALL OCCURRING LATE
THURSDAY NIGHT INTO FRIDAY MORNING.
- NORTHEAST TO NORTH WINDS WILL GUST TO 25 TO 35 MPH FRIDAY INTO
FRIDAY NIGHT, ESPECIALLY IN THE FOX VALLEY AND LAKESHORE AREAS.
- WARM AND POTENTIALLY STORMY WEATHER IS EXPECTED EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 432 AM CDT WED APR 23 2025
CLEAR TO PARTLY CLOUDY SKIES PREVAILED ACROSS THE FORECAST AREA
EARLY THIS MORNING. THE EXPECTED FOG HAS BEEN SLOW TO FORM THUS
FAR, BUT SUSPECT PATCHY FOG WILL DEVELOP TOWARD SUNRISE. DRY
CONDITIONS HELD ACROSS GRB CWA, BUT A SMALL CLUSTER OF STORMS
WITH PEA TO NICKEL SIZE HAIL WAS ONGOING ACROSS UPPER MICHIGAN
(AHEAD OF A WEAK SHORT-WAVE), AND SHOWERS AND STORMS HAD
DEVELOPED IN A MORE MOIST AND UNSTABLE AIR MASS FROM IOWA INTO N
IL.
PRECIPITATION CHANCES: A COLD FRONT (CURRENTLY OVER NW MN) WILL
APPROACH THE REGION TODAY, AND EDGE INTO NC WI LATER IN THE
AFTERNOON. AHEAD OF THE FRONT, MOISTURE WILL INCREASE, WITH PWATS
RISING TO AROUND AN INCH IN THE FOX VALLEY/LAKESHORE AREAS DURING
THE AFTERNOON. IN ADDITION, MODEST INSTABILITY (CAPE OF 300-800
J/KG AND MID-LEVEL LAPSE RATES OF 7-7.5 C/KM) WILL BUILD AHEAD OF
THE FRONT, RESULTING IN A GRADUAL INCREASE IN SHOWERS AND
SCATTERED THUNDERSTORMS DURING THE AFTERNOON. DEEP LAYER SHEAR IS
STRONG (45-65 KNOTS), SO ISOLATED STRONG STORMS COULD FORM IF
ENOUGH HEATING OCCURS. SPC SREF 40+ DBZ PAINTBALLS SHOW THE BEST
CONCENTRATION OF STORMS OCCURRING SOUTH OF A LINE FROM ISW-SUE
BETWEEN 2-7 PM, AND A FEW MODELS SUGGEST A WEAK BOUNDARY (PERHAPS
A WARM FRONT) LIFTING INTO THE FOX VALLEY DURING THIS PERIOD. SPC
HAS OUTLOOKED OUR FAR SOUTHEAST COUNTIES IN A MARGINAL RISK FOR
LARGE HAIL, AND THIS LOOKS REASONABLE. THE SHOWERS AND STORMS WILL
LINGER ACROSS THE SOUTHEAST PART OF THE FORECAST AREA INTO THE
EVENING, AND WEAK INSTABILITY/HIGH PWATS LINGERING OVER OUR
SOUTHERN COUNTIES WILL SUPPORT A SMALL CHANCE OF SHOWERS AND
STORMS THERE INTO EARLY THURSDAY MORNING.
THE PRECIPITATION FORECAST IS TRICKY FOR THURSDAY AND THURSDAY
EVENING, AS HIGH PRESSURE MAY TEND TO SUPPRESS SHOWER ACTIVITY IN
FAR NORTHERN AND EASTERN WI. HOWEVER, SEVERAL MODELS DEVELOP A
NARROW FRONTOGENETIC BAND OF SHOWERS SOMEWHERE OVER NORTHERN WI
DURING THE MORNING, WITH A GRADUAL EXPANSION OF SHOWERS NEAR THIS
FEATURE IN THE AFTERNOON AND EVENING. HAVE FOCUSED THE HIGHEST
POPS OVER AREAS WELL NORTHWEST OF THE FOX VALLEY THROUGH THE
EVENING, BUT CONFIDENCE WAS NOT HIGH ENOUGH TO FORECAST A
COMPLETELY DRY FORECAST FOR GRB AT THIS TIME. MODEL CONCENSUS
CONTINUES TO SHOW THE BEST POTENTIAL FOR WIDESPREAD SIGNIFICANT
RAINFALL OCCURRING LATE THURSDAY NIGHT INTO FRIDAY MORNING AS
WAA, A SHORT-WAVE TROUGH AND 850 MB FRONTOGENESIS MOVE THROUGH
AND LOW PRESSURE TRACKS ACROSS N IL OR S WI. WE SHOULD SEE A
DIMINISHING TREND IN THE PRECIPITATION FRIDAY AFTERNOON WITH
DRY CONDITIONS RETURNING FRIDAY EVENING AND LASTING THROUGH MOST
OF THE WEEKEND AS A LARGE HIGH PRESSURE SYSTEM BUILDS INTO THE
WESTERN GREAT LAKES.
A STRONG LOW PRESSURE SYSTEM IS EXPECTED TO LIFT NORTHWEST OF THE
REGION EARLY NEXT WEEK, AND DRAG A COLD FRONT THROUGH WI ON
TUESDAY. THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL INCREASE AS
THE FRONT APPROACHES, AND THE PATTERN SUGGESTS POTENTIAL FOR
SEVERE THUNDERSTORMS DURING THE MONDAY AFTERNOON THROUGH TUESDAY
PERIOD.
GUSTY WINDS FRIDAY INTO FRIDAY NIGHT: WINDS WILL BE LIGHT TO
MODERATE THROUGH THURSDAY. THE PRESSURE GRADIENT WILL INCREASE
BETWEEN HIGH PRESSURE OVER CANADA AND LOW PRESSURE TRACKING S/SE
OF THE FORECAST AREA FRIDAY INTO FRIDAY NIGHT. GUSTS TO 25 TO 35
MPH CAN BE EXPECTED, WITH THE HIGHEST GUSTS OCCURRING IN THE FOX
VALLEY AND LAKESHORE AREAS FRIDAY AFTERNOON AND EVENING.
TEMPERATURES: A WARMING TREND IS EXPECTED TODAY, WITH HIGHS
REACHING INTO THE MIDDLE 60S TO AROUND 70. A MODEST DROP IN
TEMPERATURES IS EXPECTED AFTER THE COLD FRONT MOVES THROUGH
TONIGHT, AND EVEN MORE COOLING IS EXPECTED AS WIDESPREAD RAIN
MOVES THROUGH THURSDAY NIGHT INTO FRIDAY. THIS SHOULD CAUSE
TEMPERATURES TO DROP A LITTLE BELOW NORMAL BY FRIDAY. PARTLY
CLOUDY SKIES WILL HELP BOOST READINGS BACK ABOVE NORMAL OVER THE
WEEKEND, WITH GUSTY S-SW WINDS AHEAD OF A COLD FRONT PUSHING
TEMPERATURES MUCH ABOVE NORMAL EARLY NEXT WEEK.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1040 PM CDT TUE APR 22 2025
MOSTLY CLEAR SKIES AND LIGHT WINDS ARE EXPECTED OVERNIGHT, WHICH
WILL ALLOW FOR SOME FOG FORMATION ACROSS THE AREA. GUIDANCE IS
STILL MIXED ON HOW DENSE/LOW VSBY WILL BE LATE TONIGHT INTO EARLY
WEDNESDAY MORNING. THE NBM INDICATES THE BEST CHANCE (40 PERCENT)
FOR MVFR CIGS IS ACROSS EAST-CENTRAL WISCONSIN WITH A 25% CHANCE
FOR IFR VSBYS LATE TONIGHT. GIVEN THE HIGHER PROBABILITIES WILL
PLACE A TEMPO GROUP FOR IFR CONDITIONS ACROSS THE EAST-CENTRAL
WISCONSIN TAFS BUT LEAVE THEM OUT OF THE CENTRAL AND NORTH-CENTRAL
WISCONSIN SITES. MODELS INDICATE THAT ONLY A FEW HOURS OF IFR
VSBYS ARE POSSIBLE, WITH FOG QUICKLY DISSIPATING AFTER SUNRISE.
VFR CONDITIONS RETURN FOR WEDNESDAY MORNING, AND SHOULD CONTINUE
INTO WEDNESDAY AFTERNOON. MODELS INDICATE SOME ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE WEDNESDAY
AFTERNOON AND EVENING, WITH THE BEST CHANCE WEDNESDAY AFTERNOON
(30-40%) ACROSS EAST-CENTRAL WISCONSIN. THEREFORE, WILL INTRODUCE
A PROB30 GROUP FOR THE FOX VALLEY EAST TO THE LAKESHORE AS MODELS
INDICATE THIS IS THE MOSTLY LIKELY AREA TO SEE THIS ACTIVITY.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....KIECKBUSCH
AVIATION.......KURIMSKI
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