701
FXUS63 KGRB 232342
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
642 PM CDT WED APR 23 2025
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
KEY MESSAGES
- A FEW THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON AND
EVENING, BUT CONFIDENCE IS LOW. ISOLATED MARGINALLY SEVERE
STORMS WITH HAIL IS THE MAIN THREAT.
- PERIODIC PRECIPITATION CHANCES CONTINUE THROUGH FRIDAY, WITH THE
BEST CHANCE OF WIDESPREAD SIGNIFICANT RAINFALL OCCURRING
THURSDAY NIGHT INTO FRIDAY MORNING. THERE IS A 40-70%
PROBABILITY OF RECEIVING A HALF AN INCH OF RAIN.
- 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.
PORTIONS OF THE AREA ARE HIGHLIGHTED FOR THE POTENTIAL FOR
SEVERE WEATHER NEXT MONDAY AND TUESDAY.
DISCUSSION
ISSUED AT 338 PM CDT WED APR 23 2025
SHORT TERM...TONIGHT AND THURSDAY
FOCUS REMAINS ON PRECIPITATION TRENDS OVER THE NEXT 24+ HOURS. AS
MORNING RAIN/CLOUDS CLEARED, THE AFTERNOON SUNSHINE GAVE
TEMPERATURES A BOOST, AND ALLOWED FOR INCREASING INSTABILITY. AT
3:00 PM, MUCAPES RANGED FROM ABOUT 300 TO 1000 J/KG, WITH MID
LEVEL LAPSE RATES OF 7 TO 7.5 C/KM, AND 0-6KM SHEAR OF 45 TO 55
KTS. CAMS HAVE NOT HAD A GOOD GRASP ON RADAR TRENDS TODAY, WITH
DIFFICULTY PICKING UP ON THE MORNING ACTIVITY. MANY WERE VIRTUALLY
DRY FOR THIS AFTERNOON AND EVENING, BUT THE 17Z AND 18Z HRRR ARE
NOW BACK TO SHOWING SOME EVENING DEVELOPING. OVERALL, THIS LEADS
TO LOW CONFIDENCE MOVING FORWARD. THERE ISN'T MUCH LARGE SCALE
FORCING, WITH THE SURFACE COLD FRONT STILL BACK ACROSS WESTERN
WISCONSIN. THERE ARE SOME SUBTLE BOUNDARIES AROUND, SO DIURNALLY
DRIVEN SHOWERS/THUNDERSTORMS, ESPECIALLY ALONG ANY BOUNDARIES,
WOULD BE THE MAIN POTENTIAL. GIVEN THE CONVECTIVE PARAMETERS,
THERE REMAINS A MARGINAL RISK FOR ISOLATED SEVERE STORMS, MAINLY
FOR 1" HAIL. THE BEST CHANCE OF THIS IS SOUTH OF A LINE FROM
WISCONSIN RAPIDS TO STURGEON BAY FROM ABOUT 6 PM TO 10 PM, WHICH
IS LATER THAN THE PREVIOUS FORECAST.
CONFIDENCE REMAINS LOW OVERNIGHT AND THURSDAY MORNING. THERE IS A
SLIGHT UPTICK IN FORCING THURSDAY MORNING, PRIMARILY FROM AN FGEN
BAND AROUND 850MB. THIS COULD CREATE SOME SCATTERED SHOWERS FOR
THE FIRST HALF OF THE DAY. INSTABILITY IS MINIMAL, WITH SOME
POCKETS OF ~100 J/KG AROUND. THEREFORE, SOME ISOLATED THUNDER IS
POSSIBLE ON THURSDAY, BUT OVERALL IT WILL JUST BE RAIN.
GREATER FORCING ARRIVES LATE THURSDAY AFTERNOON AS ANOTHER FGEN
BAND ARRIVES, ALONG WITH THE RRQ OF THE UPPER JET, AND THE SURFACE
LOW TRACKING SOUTH OF THE AREA. THIS WILL BE THE START OF MORE
WIDESPREAD RAIN INTO THURSDAY NIGHT.
LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ACTIVE PATTERN EXPECTED WITH TWO SYSTEMS TO CONTEND WITH. THE
FIRST SYSTEM WILL BE THURSDAY NIGHT INTO FRIDAY. FGEN BAND
EXPECTED TO SET UP NORTH AND WEST OF GREEN BAY, WHICH SHOULD BRING
ANOTHER ROUND OF RAIN, ESPECIALLY NORTH AND WEST OF THE FOX VALLEY
(GREEN BAY AND APPLETON) THURSDAY EVENING. MEANWHILE LOW PROSIER
IS EXPECTED TO MOVE INTO THE WESTERN GREAT LAKES BY 12Z FRIDAY,
THUS RAIN CHANCES WILL SPREAD EASTWARD INTO EAST-CENTRAL WISCONSIN
LATE THURSDAY NIGHT INTO FRIDAY MORNING. NBM PROBABILITIES WERE IN
THE 40-80% RANGE FOR A HALF INCH OR GREATER, WITH ONLY A 10-40%
CHANCE OVER AN INCH ACROSS CENTRAL AND NORTH-CENTRAL WISCONSIN.
WITH THE LOW TRACK SOUTH OF THE AREA, GUSTY NORTHERLY WINDS
ARE EXPECTED LATE THURSDAY NIGHT INTO FRIDAY NIGHT WHICH WILL
IMPACT OUTDOOR ACTIVITIES, ESPECIALLY IN NORTHEAST WISCONSIN.
CANADIAN HIGH PRESSURE WILL BUILD INTO THE REGION FRIDAY NIGHT
WITH DRY CONDITIONS EXPECTED ON SATURDAY UNDER PARTLY CLOUDY
SKIES. THE DRY CONDITIONS WILL CONTINUE ON SUNDAY, ALTHOUGH
CLOUDS WILL BE ON THE INCREASE. MODELS ARE POINTING TO ELEVATED
CONVECTION BREAKING OUT SUNDAY NIGHT INTO MONDAY AS A WARM FRONT
PUSHES NORTHWARD. THE STORM PREDICTION CENTER DAY 6 OUTLOOK HAS
PORTIONS OF AREA OUTLINED FOR THE POTENTIAL FOR SEVERE WEATHER.
IT IS NOT OFTEN WISCONSIN IS OUTLINED IN A DAY 6 SEVERE WEATHER
OUTLOOK FROM SPC> A STRONG COLD FRONT IS EXPECTED TO MOVE ACROSS
THE AREA LATER MONDAY NIGHT INTO TUESDAY MORNING, ALTHOUGH TIMING
IS ANTICIPATED TO CHANGE OVER THE COMING DAYS. NOT A REALLY
FAVORABLE TIME OF DAY FOR SEVERE WEATHER, BUT IT IS A STRONG
COLD FRONT WITH SOME DECENT DYNAMICS TO ENHANCE LIFT. IT COULD
BECOME WARM AHEAD OF THE WITH HIGHS WELL INTO THE 70S ON MONDAY.
HIGH PRESSURE WILL SLIDE EAST ACROSS THE AREA TUESDAY NIGHT,
THEN EAST OF THE AREA ON WEDNESDAY SHOULD RESULT IN DRY
CONDITIONS.
AVIATION
FOR 00Z TAF ISSUANCE
ISSUED AT 642 PM CDT WED APR 23 2025
ISOLATED THUNDERSTORMS ARE DEVELOPING OVER WEST-CENTRAL WI THIS
EVENING AHEAD OF AN APPROACHING COLD FRONT. THESE STORMS WILL MOVE
ACROSS CENTRAL WI AND INTO THE FOX VALLEY THIS EVENING BEFORE
EXITING OVER LAKE MICHIGAN AROUND 4Z. SATELLITE DATA IS CAPTURING A
FEW LIGHTNING FLASHES WITH THESE STORMS WHICH MAY PASS OVER THE
SOUTHER FOX VALLEY (OSH) BETWEEN 01/04Z. EXPECT AND STORMS TO REMAIN
SOUTH OF THE CENTRAL WI TAF SITES (CWA AND AUW). OTHERWISE NORTH AND
WEST OF THE FOX VALLEY VFR CONDITIONS ARE FORECAST THROUGH THE TAF
PERIOD. WINDS WILL SHIFT AROUND TO THE NORTHWEST BEHIND THE COLD
FRONT OVERNIGHT.
PRIMARILY VFR CONDITIONS ARE EXPECTED ON THURSDAY AS HIGH AND MID
LEVEL CLOUDS START TO MOVE INTO THE AREA AHEAD OF A LOW PRESSURE
SYSTEM FORECAST TO LIFT ACROSS NORTHERN IL. SCATTERED SHOWERS MAY
DEVELOP OVER THE FOX VALLEY DURING THE MORNING AND LIGHT NORTH AND
WEST INTO THE AFTERNOON WITH MORE WIDESPREAD PRECIPITATION ARRIVING
DURING THE LATE AFTERNOON/EVENING.
KGRB/KATW...MAIN FOCUS IN THE NEAR TERM AT KGRB AND KATW IS IF ANY
THUNDERSTORMS MOVE OVER THESE TERMINALS LATE THIS EVENING (01-04Z).
ISOLATED THUNDERSTORMS ARE DEVELOPING OVER WEST-CENTRAL WI LATE THIS
AFTERNOON, HOWEVER, RADAR TRENDS FAVOR THESE STORMS REMAINING SOUTH
OF BOTH KGRB AND KATW AS THEY MOVE EAST. FOR NOW KEEP A -SHRA IN A
PROB30 GROUP FROM 01/04Z TO ACCOUNT FOR THE POTENTIAL PRECIP, BUT
LEFT TS OUT OF BOTH TAFS. BEHIND THESE STORMS SOME CAMS SHOW A BRIEF
PERIOD OF FOG DEVELOP BEFORE A COLD FRONT MOVES THROUGH OVERNIGHT,
BUT CONFIDENCE THIS OCCURS IS TOO LOW TO INCLUDE IN EITHER TAF.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....KLJ/ECKBERG
AVIATION.......GK
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