940
FXUS63 KGRB 230809
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
309 AM CDT THU OCT 23 2025
FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE
KEY MESSAGES
- LAKE EFFECT SHOWERS WILL GRADUALLY DIMINISH TODAY OVER NORTH-
CENTRAL WISCONSIN. SNOW MAY MIX IN WITH THE RAIN AT TIMES, WHICH
WILL BRING THE FIRST SNOWFLAKES OVER FAR NORTH-CENTRAL
WISCONSIN FOR THE SEASON.
- A FREEZE WARNING HAS BEEN ISSUED FOR EAST-CENTRAL WISCONSIN
TONIGHT.
- BELOW NORMAL TEMPERATURES ARE EXPECTED THROUGH FRIDAY, FOLLOWED
BY A SLOW WARMING TREND INTO THE WEEKEND.
DISCUSSION
ISSUED AT 308 AM CDT THU OCT 23 2025
SHORT TERM...TODAY...TONIGHT...AND FRIDAY
A LARGE UPPER-LEVEL TROUGH CONTINUES TO SPIN OVER THE GREAT LAKES
REGION EARLY THIS MORNING, MAINTAINING COLD CYCLONIC FLOW ACROSS
WISCONSIN. AN ASSOCIATED THERMAL TROUGH, WITH 850MB TEMPERATURES
AROUND -4C TO -5C, IS CENTERED OVER THE WESTERN PART OF THE STATE.
LAKE EFFECT SHOWERS, POSSIBLY MIXED WITH SNOWFLAKES OVER VILAS
COUNTY, PERSIST OVER NORTH-CENTRAL WISCONSIN WHERE SURFACE
TEMPERATURES ARE IN THE MID-30S, SUPPORTED BY FAVORABLE WIND
TRAJECTORIES AND INSTABILITY OVER LAKE SUPERIOR. SHOWERS HAVE
DIMINISHED ELSEWHERE, WITH SOME PARTIAL CLEARING OBSERVED OVER
EAST-CENTRAL WISCONSIN. THE MAIN FORECAST FOCUS IN THE SHORT TERM
WILL BE THE DIMINISHING TREND IN SHOWERS AND THE POTENTIAL FOR
FROST AND FREEZE CONDITIONS TONIGHT AS THE CYCLONIC FLOW GRADUALLY
WEAKENS ITS GRIP ON THE AREA.
PRECIPITATION: LAKE EFFECT SHOWERS OFF WESTERN LAKE SUPERIOR WILL
CONTINUE ACROSS NORTH-CENTRAL WISCONSIN THIS MORNING. WITH
FAVORABLE WIND TRAJECTORIES, TEMPERATURE DIFFERENCES BETWEEN THE
LAKE AND AIR ALOFT (DELTA TS 15-17C), AMPLE LOW TO MID-LEVEL
MOISTURE, AND LAKE-INDUCED EQUILIBRIUM LEVELS REACHING UP TO 9000
FT EARLY TODAY, CONDITIONS REMAIN SUPPORTIVE FOR PRECIPITATION. AS
BOUNDARY LAYER TEMPERATURES COOL FURTHER THIS MORNING, SNOWFLAKES
ARE EXPECTED TO MIX IN WITH THE RAIN SHOWERS, PARTICULARLY OVER
FAR NORTH-CENTRAL WISCONSIN (VILAS COUNTY). THIS COULD RESULT IN
THE FIRST SNOWFLAKES OF THE SEASON FOR THESE LOCATIONS, ALTHOUGH
SIGNIFICANT ACCUMULATION OR VISIBILITY REDUCTIONS SPECIFICALLY DUE
TO SNOW ARE NOT ANTICIPATED. THESE LAKE EFFECT SHOWERS, ALONG
WITH THE RAIN/SNOW MIX POTENTIAL, WILL DIMINISH THIS AFTERNOON AS
DRIER AIR MOVES IN OVER WESTERN LAKE SUPERIOR AND EQUILIBRIUM
LEVELS LOWER.
OUTSIDE OF THE PRIMARY LAKE EFFECT ZONE IN NORTH-CENTRAL
WISCONSIN, SHOWER ACTIVITY HAS LARGELY DIMINISHED. HOWEVER,
ISOLATED SPRINKLES OR LIGHT SHOWERS REMAIN POSSIBLE, MAINLY IN THE
AFTERNOON. CLOUDS ARE EXPECTED TO BUILD ACROSS AREAS THAT SAW
CLEARING EARLY THIS MORNING BETWEEN 10 AM AND NOON AS CUMULUS
CLOUDS DEVELOP. MOST AREAS OUTSIDE OF NORTH-CENTRAL WI SHOULD SEE
IMPROVING CONDITIONS LATE THIS AFTERNOON INTO THIS EVENING AS
PARTIAL CLEARING ENSUES.
FROST/FREEZE: HIGH PRESSURE WILL BUILD INTO THE REGION TONIGHT
AND FRIDAY, LEADING TO CLEARING SKIES AND DIMINISHING WINDS
OVERNIGHT. THIS SETUP WILL PROMOTE RADIATIONAL COOLING, LEADING TO
FROST OR FREEZE POTENTIAL FOR MUCH OF THE AREA TONIGHT. A FREEZE
WARNING HAS BEEN ISSUED FROM TONIGHT INTO FRIDAY MORNING FOR AREAS
FROM OUTAGAMIE AND WINNEBAGO COUNTIES EASTWARD TO THE LAKESHORE,
EXCLUDING THE DOOR PENINSULA WHERE LAKE INFLUENCE AND BREEZY
CONDITIONS WILL KEEP TEMPERATURES SLIGHTLY WARMER. CONFIDENCE IN
WIDESPREAD FROST IS MEDIUM DUE TO SOME UNCERTAINTY ABOUT WHETHER
WINDS WILL FULLY DECOUPLE OVERNIGHT. PROBABILITIES FOR LOWS
REACHING 32 DEGREES ARE ESTIMATED BETWEEN 40-60% ACROSS EAST-
CENTRAL WISCONSIN WITHIN THE WARNING AREA.
LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
LOW IMPACT WEATHER IS GENERALLY EXPECTED THIS WEEKEND THROUGH THE
MIDDLE OF NEXT WEEK. A PROGRESSIVE SPLIT FLOW PATTERN WILL MOVE
ACROSS THE GREAT LAKES THIS WEEKEND. A MODEST, COMPACT SHORTWAVE
DISTURBANCE TRACKING THROUGH THE NORTHERN STREAM MAY BRING
SCATTERED LIGHT RAIN SHOWERS TO THE AREA ON SATURDAY. CONFIDENCE
IN THIS SYSTEM REMAINS BELOW NORMAL, THOUGH CHANCES HAVE SLIGHTLY
INCREASED RECENTLY.
TEMPERATURES WILL UNDERGO A MODEST WARMUP THROUGH THE WEEKEND,
WITH HIGH TEMPERATURES REACHING THE MIDDLE TO UPPER 50S BY SUNDAY
UNDER PARTLY TO MOSTLY SUNNY SKIES AS HIGH PRESSURE BRIEFLY
INFLUENCES THE REGION.
EARLY NEXT WEEK, MODEL GUIDANCE SUGGESTS STRONG UPPER-LEVEL JET
ENERGY ASSOCIATED WITH THE NEXT TROUGH DIGGING INTO THE WESTERN US
WILL SPUR SURFACE CYCLOGENESIS OVER THE CENTRAL OR NORTHERN PLAINS
BY MONDAY. THIS DEVELOPING LOW-PRESSURE SYSTEM IS EXPECTED TO
TRACK EASTWARD, PUSHING A FRONTAL SYSTEM ACROSS THE REGION AROUND
THE TUESDAY-WEDNESDAY TIMEFRAME. THIS SYSTEM IS LIKELY TO BRING
ANOTHER ROUND OF SHOWERS, POTENTIALLY ACCOMPANIED BY BREEZY WINDS,
TO NORTH-CENTRAL AND NORTHEAST WISCONSIN. TEMPERATURES ARE
EXPECTED TO COOL DOWN AGAIN BEHIND THIS SYSTEM TOWARDS THE MIDDLE
OF NEXT WEEK. CONFIDENCE IN THE EXACT TIMING AND STRENGTH OF THIS
EARLY-TO-MIDWEEK SYSTEM REMAINS SOMEWHAT UNCERTAIN, TYPICAL FOR
THIS FORECAST RANGE, BUT TRENDS SUGGEST INCREASING CHANCES FOR
PRECIPITATION AND WIND DURING THAT PERIOD.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1003 PM CDT WED OCT 22 2025
LAKE EFFECT SHOWERS CONTINUE OVER NORTHERN WI, INCLUDING AT RHI,
BUT OTHERWISE HAVE DIMINISHED OVER THE REST OF THE AREA. EXPECT
MAINLY VFR CONDITIONS THE REST OF THE NIGHT FROM CENTRAL TO EAST-
CENTRAL WI. MEANWHILE, IFR TO LOWER MVFR CONDITIONS WILL PERSIST
OVER NORTHERN WI.
ON THURSDAY, AS COLDEST AIR ALOFT MOVES OVERHEAD, STILL LIKE
FEW HOUR PERIOD OF MAINLY SNOW AT RHI CENTERED AROUND 14Z (IFR
VSBY POSSIBLE), BEFORE THE LAKE EFFECT SHOWERS START TO END. IT
SHOULD STAY DRY ELSEWHERE. CIGS WILL STAY MVFR OVER THE NORTH
(RHI), FEATURE A MIX OF MVFR AND VFR OVER CENTRAL WI (AUW/CWA),
AND STAY VFR FOX VALLEY TO THE LAKESHORE (GRB/ATW/MTW). SKIES WILL
FINALLY START TO CLEAR OUT ON THURSDAY EVENING, THOUGH LOWER VFR
CIGS WILL PROBABLY HANG ON AT RHI TIL THE END OF THE TAF PERIOD.
NORTHWEST WINDS WILL BE LIGHT TONIGHT, BUT WILL START TO GUST TO
AROUND 15 KTS MID MORNING INTO MID AFTERNOON. WINDS WILL BECOME
LATE THURSDAY AFTERNOON, SETTING THE STAGE FOR WIDESPREAD FROST OR
FREEZE ON THURSDAY NIGHT.
GRB WATCHES/WARNINGS/ADVISORIES
FREEZE WARNING FROM 2 AM TO 9 AM CDT FRIDAY FOR WIZ038>040-
048>050.
DISCUSSION.....MPC
AVIATION.......JLA
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