650
FXUS63 KGRB 190023 AAA
AFDGRB
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GREEN BAY WI
723 PM CDT FRI APR 18 2025
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
AND NEW INFORMATION ADDED TO UPDATE SECTION
UPDATE
ISSUED AT 719 PM CDT FRI APR 18 2025
CONDITIONS HAVE BECOME MORE STABLE IN WAKE OF THE COLD FRONT THAT
HAS SHIFTED SOUTH AND EAST OF NORTHEAST WI. HAD ISOLATED THUNDER
EARLIER THIS EVENING, BUT FOCUS FOR THIS HAS MOVED INTO LOWER
MICHIGAN. ELEVATED INSTABILITY THAT IS STILL PRESENT (200-400
J/KG OF MUCAPE) SEEMS TO BE JUST HELPING TO ENHANCE THE LIGHT RAIN
AND SHOWERS OVER THE AREA. AN ISOLATED LIGHTNING STRIKE MAY STILL
OCCUR THROUGH LATE EVENING OVER CALUMET AND MANITOWOC COUNTIES AS
SPOTTY CONVECTION IN SOUTHERN WI ON NORTHERN EDGE OF HIGHER SFC
BASED CAPES EASES EAST-NORTHEAST, BUT THIS TOO WILL BE MINIMAL IN
COVERAGE. THUS HAVE DIALED BACK THUNDER MENTION TO FAR SOUTHEAST
CWA AND WENT WITH MURKIER LIGHT RAIN/LIGHT FOG IDEA OVER THE AREA
THE REST OF THE EVENING. UPDATED HWO TO REMOVE ANY MENTION OF
STRONG THUNDERSTORMS. THAT ALL LINES UP WITH LATEST SPC DAY1
OUTLOOK WHICH NOW HAS THE MARGINAL RISK LINE (LEVEL 1 OF 5) TO THE
SOUTHEAST OF GRB FORECAST AREA.
KEY MESSAGES
- THUNDERSTORM RISK FOR THIS EVENING HAS DIMINISHED. 10-20 PERCENT
CHANCE OF A THUNDERSTORM THROUGH LATE EVENING OVER CALUMET AND
MANITOWOC COUNTIES.
- NEXT CHANCES FOR WIDESPREAD PRECIPITATION ARRIVE SUNDAY NIGHT
INTO MONDAY. MIXED PRECIP TYPES POSSIBLE, MAINLY ACROSS NORTH-
CENTRAL WISCONSIN.
DISCUSSION
ISSUED AT 234 PM CDT FRI APR 18 2025
CLOUDY TO MOSTLY CLOUDY SKIES AND LOW CEILINGS CONTINUE TO PLAGUE
THE FORECAST AREA LATE THIS AFTERNOON. DESPITE THESE CONDITIONS,
CAMS MODELS CONTINUE TO DEVELOP SHOWERS, AND A FEW THUNDERSTORMS,
ACROSS THE AREA LATE THIS AFTERNOON AND THIS EVENING. MESOANALYSIS
SHOWS THAT DESPITE VERY STRONG SHEAR ACROSS THE REGION, WITH BULK
SHEAR VALUES OF 75 KNOTS, INSTABILITY IS WANTING ACROSS OUR AREA
WITH THE BEST INSTABILITY WELL TO OUR SOUTH IN NORTHERN ILLINOIS
AND ONLY A FEW HUNDRED J/KG OF MUCAPE ACROSS OUR AREA. THEREFORE,
WHILE THUNDERSTORMS WILL BE POSSIBLE, SEVERE WEATHER IS NOT
ANTICIPATED ACROSS OUR AREA THIS EVENING AS ANY THUNDERSTORMS THAT
DEVELOP SHOULD BE ELEVATED IN NATURE.
HIGH PRESSURE WILL PROVIDE A BREAK IN THE ACTIVE PATTERN LATE
TONIGHT THROUGH SUNDAY MORNING AS IT TRACKS ACROSS THE NORTHERN
GREAT LAKES. MEANWHILE, A LOW PRESSURE SYSTEM DEVELOPING ACROSS
THE SOUTHERN PLAINS WILL TRACK NORTH-NORTHEAST TOWARDS THE WESTERN
GREAT LAKES REGION SUNDAY NIGHT AND MONDAY. SOME LIGHT RAIN IS
POSSIBLE SUNDAY AFTERNOON AHEAD OF THE MAIN LOW WITH ISENTROPIC
LIFT ACROSS THE REGION; HOWEVER, THE MAIN SWATH OF PRECIPITATION
IS EXPECTED TO HOLD OFF UNTIL SUNDAY NIGHT AND MONDAY.
PRECIPITATION WITH THIS SYSTEM SHOULD MAINLY BE RAIN ACROSS MUCH
OF THE AREA, WITH A MIX OF RAIN AND SNOW ACROSS NORTH-CENTRAL
WISCONSIN. THE LATEST PROBABILISTIC GUIDANCE HAS CUT BACK ON THE
AMOUNT OF SNOW QUITE A BIT THIS RUN WITH ONLY A 10-20% CHANCE OF 2
INCHES OR MORE OF SNOW ACROSS FAR NORTH-CENTRAL WISCONSIN AND A
20-40% CHANCE OF AN INCH OR MORE OF SNOW.
AFTER A BRIEF BREAK IN THE ACTION LATE MONDAY NIGHT INTO TUESDAY
MORNING, THE NEXT SYSTEM WILL TRACK THROUGH THE REGION TUESDAY
AFTERNOON INTO TUESDAY NIGHT. THIS SYSTEM WILL HAVE FAIRLY WEAK
DYNAMICS; THEREFORE, ONLY LIGHT RAIN IS EXPECTED FROM THIS NEXT
LOW PRESSURE SYSTEM. YET ANOTHER LOW PRESSURE SYSTEM LOOKS TO
AFFECT THE AREA WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. BEYOND
THIS PART OF THE FORECAST THERE IS QUITE A BIT OF UNCERTAINTY AS
THERE ARE DISCREPANCIES ON IF A CANADIAN HIGH PRESSURE CAN KEEP
THE WEATHER DRY TO END NEXT WEEK.
AVIATION
FOR 00Z TAF ISSUANCE
ISSUED AT 719 PM CDT FRI APR 18 2025
IN WAKE OF THE COLD FRONT THAT HAS MOVED THROUGH, CONDITIONS HAVE
BECOME MORE STABLE. THUS THE RISK OF ANY THUNDERSTORMS FOR THE
REST OF THE EVENING IS LOW. MVFR-LOW VFR STRATUS WITH PATCHY LIGHT
RAIN AND LIGHT FOG (MVFR-VFR VISIBILITY) TO START THE EVENING
WILL DETERIORATE TO MAINLY IFR TO MVFR CONDITIONS BY LATE EVENING.
LATE TONIGHT, EXPECT CONDITIONS TO STAY IFR OVER NORTHERN WI WITH
RAIN/SNOW SHOWERS AND FOG, BUT ELSEWHERE CIGS SHOULD LIFT TO MVFR
AND VISIBILITY WILL IMPROVE TO VFR.
ON SATURDAY, WITH NORTHERLY FLOW, MVFR-VFR CONDITIONS IN THE
MORNING WILL IMPROVE TO VFR IN THE AFTERNOON AS CLOUDS SCATTER
OUT. WINDS TURN SOUTHEAST ON SATURDAY NIGHT WHICH COULD BRING
SCATTERED MVFR CLOUDS BACK INTO PICTURE FROM LAKESHORE TO THE FOX
VALLEY. VFR CONDITIONS WILL OCCUR ELSEWHERE.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE.........JLA
DISCUSSION.....KURIMSKI
AVIATION.......JLA
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