968
FXUS63 KGRB 021808
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
108 PM CDT WED JUL 2 2025
UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE
KEY MESSAGES
- THERE IS A CHANCE OF THUNDERSTORMS THIS AFTERNOON, ESPECIALLY
OVER NORTHERN WI. A FEW STORMS MAY BECOME STRONG TO MARGINALLY
SEVERE, ESPECIALLY IN FAR NORTHEAST WI BETWEEN 2 PM AND 8 PM.
- ADDITIONAL CHANCES FOR RAIN AND STORMS WILL BE POSSIBLE THURSDAY
THROUGH THE HOLIDAY WEEKEND, WITH THE BEST CHANCE FOR WIDESPREAD
SHOWERS AND THUNDERSTORMS OCCURRING SATURDAY AND SATURDAY NIGHT.
THERE SHOULD BE A BREAK IN THE THUNDERSTORM CHANCES FOR 4TH OF
JULY FIREWORKS DISPLAYS (FRIDAY EVENING).
- TEMPERATURES WILL BE ABOVE NORMAL THROUGH THE HOLIDAY WEEKEND,
WITH VERY WARM AND HUMID CONDITIONS (HEAT INDICES IN THE UPPER
80S TO MIDDLE 90S) ARRIVING FOR THE 4TH OF JULY.
DISCUSSION
ISSUED AT 346 AM CDT WED JUL 2 2025
CLEAR TO PARTLY CLOUDY SKIES WERE OBSERVED ACROSS GRB CWA EARLY
THIS MORNING. TEMPERATURES RANGED FROM THE MIDDLE TO UPPER 50S
NORTHWEST TO AROUND 70 SOUTHEAST. WV IMAGERY SHOWED A SHORT-WAVE
TROUGH MOVING THROUGH SW ONTARIO AND NORTHERN MN, ACCOMPANIED BY A
CLUSTER OF SHOWERS AND EMBEDDED THUNDERSTORMS. THESE SHOWERS
SHOULD REACH NORTH CENTRAL WI TOWARD MIDDAY.
THUNDERSTORM AND SEVERE WEATHER POTENTIAL THIS AFTERNOON: THE
SHORT-WAVE OVER NORTHERN MN WILL TRACK THROUGH NORTHERN WI THIS
AFTERNOON, GENERATING SHOWERS AND SCATTERED THUNDERSTORMS. THERE
WILL BE SOME INGREDIENTS IN PLACE FOR SEVERE WEATHER, INCLUDING
CAPE OF 1-2K J/KG, DEEP LAYER SHEAR OF 30 TO 35 KNOTS AND
INVERTED-V SOUNDINGS. HOWEVER, THE STRONGEST FORCING WILL OVERLAP
WITH THE LOWEST CAPE VALUES OVER NORTHERN WI, SO OVERALL
CONFIDENCE IN SEVERE STORMS IS LOW. SPC HREF 40+ DBZ PAINTBALLS
AND MAX WIND SPEEDS, AND SIMULATED REFLECTIVITIES OFF THE CAMS,
SHOWED THE MOST ORGANIZED CONVECTION OCCURRING IN FAR NE WI, IN
THE VICINITY OF A WEAK CONVERGENCE ZONE/SURFACE TROUGH. WILL FOCUS
MESSAGING FOR SEVERE STORMS MAINLY OVER THAT REGION BETWEEN 2 PM
AND 8 PM, EVEN THOUGH THE SPC MARGINAL RISK COVERS THE ENTIRE CWA.
COVERAGE OF THE SHOWERS AND STORMS SHOULD BE LESS FARTHER SOUTH
DUE TO WEAKER FORCING. THE MAIN AREA OF SHOWERS AND STORMS SHOULD
SHIFT EAST OF THE REGION BY EARLY EVENING, BUT MODELS SUGGEST
CONTINUED WEAK DEVELOPMENT OCCURRING ALONG A WEAK FRONTAL BOUNDARY
AS IT SAGS SOUTH DURING THE EVENING AND EARLY OVERNIGHT.
THUNDERSTORM CHANCES THROUGH THE HOLIDAY WEEKEND: THE WEAK FRONT
IS EXPECTED TO SAG SOUTHWEST OF THE REGION BY THURSDAY, THEN STALL
OUT THROUGH THURSDAY NIGHT. DESPITE A MOIST AND UNSTABLE AIR MASS
OVER THE SOUTHWEST PART OF THE FORECAST AREA, MODELS DON'T SHOW
MUCH CONVECTION DEVELOPING, LIKELY DUE TO VERY WEAK LOW-LEVEL FLOW
ASCENDING THE FRONTAL ZONE AND OVERALL WEAK FORCING. WILL ONLY
CARRY SLIGHT CHANCE/CHANCE POPS FOR THE SOUTHWEST CWA DURING THIS
PERIOD.
THE WARM FRONT IS FINALLY EXPECTED TO LIFT NORTHEAST THROUGH THE
FORECAST AREA ON THE 4TH OF JULY, THOUGH CONVECTIVE COVERAGE WILL
BE LIMITED DUE TO A BUILDING UPPER LEVEL RIDGE OVER THE WESTERN
GREAT LAKES. AFTER THE WARM FRONT LIFTS THROUGH, GENERALLY DRY
CONDITIONS ARE EXPECTED FOR EVENING FIREWORKS DISPLAYS.
SOUTHWEST FLOW, A STRONGER SHORT-WAVE TROUGH AND COLD FRONTAL
PASSAGE WILL BRING A MORE WIDESPREAD PERIOD OF SHOWERS AND STORMS
SATURDAY AND SATURDAY NIGHT. INSTABILITY (800-1500 J/KG) AND DEEP
LAYER SHEAR (20-30 KNOTS) WILL BE MARGINAL, AND WIDESPREAD CLOUD
COVER AND SHOWERS COULD LIMIT STRONG TO SEVERE THUNDERSTORM
DEVELOPMENT. PWATS IN EXCESS OF 2 INCHES SUGGEST POTENTIAL FOR
VERY HEAVY RAINFALL DURING THIS PERIOD. THERE IS DISAGREEMENT
ON HOW QUICKLY THE COLD FRONT WILL CLEAR THE REGION, BUT ONCE IT
DOES, THERE SHOULD BE A QUIETER/DRIER PERIOD FOR AT LEAST A DAY OR
TWO.
TEMPERATURES: ABOVE NORMAL TEMPERATURES ARE EXPECTED THROUGH
SATURDAY, FOLLOWED BY NEAR TO A LITTLE BELOW NORMAL CONDITIONS
THROUGH THE MIDDLE OF NEXT WEEK. VERY WARM AND MUGGY CONDITIONS
ARRIVE FOR THE 4TH OF JULY, WITH HEAT INDICES RISING INTO THE
UPPER 80S TO MIDDLE 90S DURING THE AFTERNOON. MILD AND MUGGY
CONDITIONS WILL PERSIST THROUGH THE EVENING FIREWORKS DISPLAYS.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 107 PM CDT WED JUL 2 2025
AS OF 18Z VFR CONDITIONS WERE NOTED AREA-WIDE WITH AFTERNOON CU
STARTING TO DEVELOP WITH BASES AROUND 4-7KFT. MEANWHILE, MORE
SUBSTANTIAL CU AND WEAK PRECIP RETURNS WERE NOTED IN NORTH-CENTRAL
WI IN ASSOCIATION WITH A SHORTWAVE COMING THROUGH. MODELS HAVE
VARIED ON THE HANDLING OF AFTERNOON PRECIP, BUT GIVEN THE CURRENT
DEVELOPMENT HAVE FOLLOWED THE MESO MODELS WHICH SHOW THIS. A
BROKEN LINE OF SHOWERS AND SOME STORMS WILL LIKELY DEVELOP ACROSS
NORTHERN WI, AND TRACK SOUTH THROUGH THE AFTERNOON AND EARLY
EVENING. INCLUDED MOST LIKELY TIMING OF RAIN/STORMS IN PROB30
GROUPS, ALTHOUGH TEMPO FOR KRHI WHERE COVERAGE WILL BE A LITTLE
BETTER. DIPS TO MAINLY MVFR LIKELY WITHIN ANY HEAVIER RAIN AND
THUNDERSTORMS.
ACTIVITY CLEARS OUT MID-EVENING, ALTHOUGH STILL SEEING HINTS AT A
FEW WIDELY SCATTERED SHOWERS OVERNIGHT. LIKELIHOOD TOO LOW IN
INCLUDE IN TAFS, BUT A FEW MAY BE AROUND. MEANWHILE, FOG
DEVELOPMENT ACROSS CENTRAL AND NORTH-CENTRAL WI LATE TONIGHT WILL
LIKELY BRING VSBYS DOWN TO IFR LEVELS FOR A COUPLE HOURS.
WINDS WILL GENERALLY BE FROM THE WEST AROUND 5-10 KTS THROUGH
MID- EVENING, AND THEN SUBSIDE TO LIGHT IN VARIABLE, SETTLING TO
THE E/SE ON THURSDAY. GUSTS OF 30-40+ KNOTS COULD OCCUR WITHIN ANY
THUNDERSTORMS.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....KIECKBUSCH
AVIATION.......KLJ
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