507
FXUS63 KGRB 170328
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1028 PM CDT SAT AUG 16 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
KEY MESSAGES
- MAINLY DRY WEATHER EXPECTED TONIGHT INTO SUNDAY EVENING.
- INCREASING NORTHEAST WINDS AND WAVES WILL RESULT IN HAZARDOUS
CONDITIONS FOR BOATERS AND SWIMMERS ON LAKE MICHIGAN SOUTH OF
STURGEON BAY SUNDAY INTO MONDAY. A SMALL CRAFT ADVISORY AND
BEACH HAZARDS STATEMENT HAVE BEEN ISSUED.
- 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 06Z TAF ISSUANCE
ISSUED AT 1009 PM CDT SAT AUG 16 2025
LOW CLOUDS AND PATCHY DENSE FOG OVERNIGHT INTO EARLY SUNDAY WILL
BE THE PRIMARY AVIATION CONCERNS.
MAINLY DRY CONDITIONS ARE EXPECTED THROUGH MOST OF THE TAF PERIOD.
DEVELOPING NE WINDS WILL PULL LOW CLOUDS SOUTH ACROSS THE
FORECAST AREA OVERNIGHT. BEFORE THIS HAPPENS, PATCHY DENSE FOG
WILL FORM FOR A FEW HOURS WHEREVER CLEARING AND LIGHT WINDS EXIST.
THIS FOG WILL LIKELY BE MOST PERSISTENT IN CENTRAL WI, WHERE IT
COULD LINGER UNTIL 13Z-14Z/SUN. PERHAPS THE TOUGHEST PART OF THE
FORECAST WILL BE DETERMINING HOW QUICKLY THE LOW CLOUDS WILL
SCATTER OUT OR RISE TO VFR ON SUNDAY. IMPROVEMENT SHOULD ARRIVE
AT RHI EARLY TO MID MORNING, BUT IT MIGHT BE EARLY TO MID-
AFTERNOON BEFORE IT OCCURS IN PARTS OF CENTRAL AND EAST CENTRAL
WI.
THE NE WINDS WILL BECOME GUSTY LATE TONIGHT INTO SUNDAY,
ESPECIALLY IN THE FOX VALLEY AND LAKESHORE AREAS.
MAY CONSIDER ADDING SOME SHOWERS AT THE WESTERN TAF SITES LATE
SUNDAY EVENING, AS MOISTURE AND ELEVATED INSTABILITY RETURN.
GRB WATCHES/WARNINGS/ADVISORIES
BEACH HAZARDS STATEMENT FROM 10 AM CDT SUNDAY THROUGH MONDAY
AFTERNOON FOR WIZ040-050.
DISCUSSION.....KLJ
AVIATION.......KIECKBUSCH
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