305
FXUS63 KGRB 162122
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
422 PM CDT SAT AUG 16 2025
FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE
KEY MESSAGES
- LINGERING NON-SEVERE THUNDERSTORMS AND SHOWERS FOR THE NEXT
COUPLE HOURS, THEN PRECIPITATION CHANCES DECREASE FOR THE REST
OF THE WEEKEND.
- THE NEXT OPPORTUNITY FOR THUNDERSTORMS AND HEAVY RAIN IS MONDAY
AND MONDAY NIGHT AS A FRONT MOVES BACK NORTH AS A WARM FRONT.
SEVERE STORMS AND LOCALIZED FLOODING ARE POSSIBLE.
DISCUSSION
ISSUED AT 422 PM CDT SAT AUG 16 2025
THE ATMOSPHERE CONTINUES TO EVOLVE THIS AFTERNOON WITH REPEATED
ROUNDS OF CONVECTION, BUT SEEING SOME AGREEMENT THAT AFTER THIS
CURRENT ROUND OF RAIN AND THUNDERSTORMS DEPARTS, WE'LL ENTER A
MOSTLY DRY PERIOD THROUGH SUNDAY.
ONE ROUND OF RAIN AND STORM WENT THROUGH NEARLY THE ENTIRE AREA
FROM ABOUT 8AM-2PM TODAY, BRINGING ANYWHERE FROM 0.10-2.50 INCHES
OF RAIN, WITH THE HIGHER TOTALS OF 1.5"+ GENERALLY LOCATED IN A
LINE SOUTHWEST OF WAUSAU TO CLINTONVILLE. ONLY MINOR STREET
FLOODING WAS REPORTED. ISOLATED STRONG/DAMAGING WINDS OF ~60 MPH
WERE ALSO MEASURED AND REPORTED, BUT MOST PLACES SAW PEAK WIND
GUSTS CLOSER TO 30-40 MPH.
DESPITE THE MINIMAL RECOVERY TIME, JUST AS THE FIRST ROUND EXITED
TO THE EAST, A MID- LEVEL SHORTWAVE HELPED DEVELOP A SECONDARY
AREA OF CONVECTION IN WEST-CENTRAL WI, WHICH QUICKLY MOVED EAST
AND THROUGH CENTRAL WI. THIS LINE IS MOVING EAST, BUT THE
STRONGEST PORTION ON THE SOUTHERN END IS DIVING S/SE TOWARDS
SOUTHERN WI ALONG THE INSTABILITY GRADIENT. MUCAPE AT 21Z IN THE
SOUTHERN GRB FORECAST AREA RANGED FROM 400-600 J/KG, WITH 100-200
J/KG OF CIN. THEREFORE, THE LIKELIHOOD OF ANY SEVERE STORMS IS
LOW. COULD STILL SEE SOME WIND GUSTS OF 30-40 MPH ALONG THE
LEADING EDGE OF THESE STORMS, ALONG WITH BRIEF, HEAVY RAIN AND
LIGHTNING.
REST OF TODAY THROUGH SUNDAY...TRACKING THE BACK EDGE OF THE
LIGHTNING, MOST OF THIS SHOULD CLEAR THE AREA (MAINLY EAST-CENTRAL
WI) BY ABOUT 2230Z. SCATTERED, LIGHT RAIN SHOWERS WILL LINGER A
LITTLE LONGER AS THE SHORTWAVE MOVES ACROSS NORTHERN WI, AND A
SURFACE FRONT SAGS SOUTH ACROSS THE STATE. BUT, AT THIS POINT
THERE ISN'T MUCH INSTABILITY LEFT TO WORK WITH FOR ADDITIONAL
THUNDERSTORMS IN THE GRB FORECAST AREA.
THERE IS DECENT AGREEMENT THAT THIS COLD FRONT REACHES SOUTHERN
WI/NORTHERN IL TONIGHT, AND THEN HANGS OUT THERE FOR SUNDAY. THIS
WOULD ALLOW FOR MAINLY DRY CONDITIONS THROUGH LATE SUNDAY NIGHT.
MONDAY/MONDAY NIGHT...THIS FRONT AND THE ASSOCIATED SFC LOW MOVES
BACK NORTH AS A WARM FRONT ON MONDAY MORNING, BRINGING IN MORE
MOIST AND UNSTABLE AIR TO THE AREA. THERE IS VARIATION OF HOW FAR
NORTH THE FRONT GETS, BUT LOCATIONS ALONG AND SOUTH OF THIS FRONT
WILL BE PRIMED FOR MORE RAIN AND THUNDERSTORMS. CAPES OF
1000-2000+ J/KG, BULK SHEAR OF 30-40 KTS, SRH 200+ M2/S2, AND
PWATS OF 1.6-2.2" MAKE THIS SETUP CAPABLE OF PRODUCING SEVERE
STORMS WITH ALL HAZARDS, AND HEAVY RAIN/LOCALIZED FLOODING. THE
PROBABILITIES FOR AT LEAST 2" INCHES OF RAIN RANGE FROM ABOUT
5-25%, HIGHEST IN CENTRAL WI.
MID TO LATE WEEK...HIGH PRESSURE BUILDS IN ON TUESDAY BRINGING A
COUPLE DAYS OF DRY AND QUIET WEATHER. AN UPPER LOW APPROACHES THE
AREA LATE IN THE WEEK COULD BRING IN SOME PRECIP CHANGES AT TIMES.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 137 PM CDT SAT AUG 16 2025
MAIN FOCUS IS ON PRECIP/THUNDERSTORM CHANCES THROUGHOUT THE TAF
PERIOD. SEVERAL CLOUD LAYERS ARE CURRENTLY PRESENT ACROSS CENTRAL
AND NORTHEAST WI, WHICH HAVE RESULTED IN FLYING CONDITIONS RANGING
FROM VFR-LIFR, AND SITES VARYING BETWEEN THE CATEGORIES AS THE
CURRENT AREA OF CONVECTION MOVES THROUGH DUE TO LOWER CLOUD BASES
AND REDUCED VSBYS FROM HEAVIER RAINS.
FOR THE NEXT 2-4 HOURS EXPECT MINOR IMPROVEMENTS AS THIS FIRST
ROUND OF STORMS MOVES EAST. HOWEVER, THERE REMAINS LIGHTER RAIN
BEHIND THIS MAIN SYSTEM, AND SIGNS OF MORE DEVELOPMENT IS
STARTING TO MATERIALIZE FARTHER WEST ACROSS EASTERN MN/WESTERN WI.
THERE IS STILL UNCERTAINTY ON THE LEVEL OF REDEVELOPMENT THIS
AFTERNOON/EVENING, ALONG WITH THE BEST LOCATION. CURRENT
ENVIRONMENTAL ANALYSIS WOULD FAVOR JUST SOUTH OF THE GRB FORECAST
AREA. THE MOST LIKELY LOCATIONS TO SEE EVENING STORMS IS ACROSS
THE FOX VALLEY AND EAST-CENTRAL WI. HAVE CONTINUED TO INCLUDE
TEMPO/PROB30 GROUPS FOR A FEW HOURS LATE THIS AFTERNOON AND
EVENING.
AFTER THIS SECOND ROUND OF STORMS, QUIETER WEATHER IS EXPECTED
THROUGH THE TAF PERIOD, BUT LOWER CIGS AND OVERNIGHT FOG COULD
LEAD TO SOME MVFR/IFR CONDITIONS OVERNIGHT AND EARLY SUNDAY
MORNING.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....KLJ
AVIATION.......KLJ
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