530
FXUS63 KGRB 150413
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1113 PM CDT THU AUG 14 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
KEY MESSAGES
- RELATIVELY TYPICAL LATE SUMMER WEATHER EXPECTED THROUGH FRIDAY
WITH A SLIGHT CHANCE OF SHOWERS (LESS THAN 25%) OVER NORTH-
CENTRAL WISCONSIN LATE TONIGHT AND FRIDAY.
- MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED FROM
LATE FRIDAY NIGHT THROUGH MONDAY NIGHT. THERE IS A LEVEL 2 OF
5 RISK FOR SEVERE STORMS FRIDAY NIGHT, BUT CONFIDENCE IS STILL
LOW WITH REGARD TO TIMING/PLACEMENT.
- WITH HIGH RAINFALL RATES LIKELY IN ANY STORMS, THE RISK FOR
FLOODING MAY INCREASE IF REPEATED ROUNDS OF STORMS IMPACT THE
SAME AREAS. PROBABILITIES FOR AT LEAST 2 INCHES OF RAIN ARE 30
TO 60% THROUGH EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 150 PM CDT THU AUG 14 2025
THIS WEEKEND INTO EARLY NEXT WEEK: SEVERE STORM/HEAVY RAIN POTENTIAL
RELATIVELY BENIGN WEATHER APPEARS LIKELY THROUGH MUCH OF FRIDAY. A
WEAK SHORTWAVE TROUGH WILL CROSS THE REGION TONIGHT BUT THE
INSTABILITY AXIS WILL REMAIN OFF TO THE WEST WITH DRY LOW-LEVEL AIR
TO CONTEND WITH. THAT SAID, SMALL (20-30%) SHOWER CHANCES EXIST
ESPECIALLY OVER CENTRAL INTO NORTH-CENTRAL WISCONSIN TONIGHT.
MOISTURE/INSTABILITY WILL BE ON THE INCREASE LATER FRIDAY AND INTO
THE WEEKEND WITH A SERIES OF WEAK WAVES ON THE PERIPHERY OF THE
RIDGE INTERACTING WITH A FRONTAL BOUNDARY AND AMPLE RESERVOIR OF
MOISTURE/INSTABILITY TO GENERATE ROUNDS OF SHOWERS AND STORMS ACROSS
THE UPPER MIDWEST. SUFFICIENT DEEP LAYER SHEAR WOULD EXIST FOR
SOME SEVERE WEATHER POTENTIAL, WITH THE GREATEST INSTABILITY
FORECAST ON SATURDAY. THE MACHINE LEARNING SEVERE GUIDANCE
GENERALLY SUGGESTS THE HIGHER SEVERE WEATHER POTENTIAL LOCALLY FOCUSED
FRIDAY EVENING THROUGH SATURDAY NIGHT WITH THE RISK GRADUALLY
DROPPING SOUTHWARD INTO EARLY NEXT WEEK, POTENTIALLY UNDER THE
INFLUENCE OF CANADIAN HIGH PRESSURE TO THE NORTH AND A SOUTHWARD
SHIFT OF THE CONVECTIVELY REINFORCED SURFACE BOUNDARY/HIGHER
INSTABILITY.
HONING IN ON FRIDAY A BIT MORE, SOME OF THE 14.12Z HREF MEMBERS
SUGGEST POTENTIAL FOR MCS DEVELOPMENT LATE FRIDAY/FRIDAY NIGHT
AS SURFACE-BASED INSTABILITY BUILDS NORTHEAST. NEBULOUS FORCING
(BROAD WARM ADVECTION, POSSIBLE WEAK WAVE) AND WARMING MID-
LEVELS LIMITS CONFIDENCE, BUT A CONDITIONALLY FAVORABLE
ENVIRONMENT EXISTS, ESPECIALLY ON THE EDGE OF STRONGER
CAPPING/INSTABILITY. SPC BROADENED THE LEVEL 1 RISK OF SEVERE
STORMS ACROSS MUCH OF THE AREA WITH A LEVEL 2 RISK ACROSS
CENTRAL WISCONSIN WHERE SOMEWHAT BETTER AGREEMENT EXISTS WITHIN
CAM SOLUTIONS THIS MORNING.
OVERALL, CONVECTIVE DETAILS IN THIS TYPE OF PATTERN FEATURING
RELATIVELY WEAK, SUBTLE FORCING AND PLENTY OF INSTABILITY IS
LOW, AND DAY-TO-DAY CONVECTIVE TRENDS WILL INFLUENCE SUBSEQUENT
CONVECTIVE DEVELOPMENT.
THE ENVIRONMENT WILL BE VERY FAVORABLE FOR HEAVY RAINFALL WITH THE
NAEFS INDICATING PRECIPITABLE WATER VALUES BETWEEN THE 90TH-99TH
PERCENTILE LATE FRIDAY INTO TUESDAY. WARM CLOUD DEPTHS WILL LIKELY
EXCEED 4KM BY FRIDAY NIGHT WITH THE AFOREMENTIONED RESERVOIR OF
AMPLE INSTABILITY IN PLACE. THESE CONDITIONS WILL BE VERY FAVORABLE
FOR HIGH RAINFALL RATES FROM ANY CONVECTIVE SYSTEMS WITH THE
EPS/GEFS/CMC ENSEMBLES SHOWING THE FOOTPRINT OF HIGHEST CHANCES FOR
AT LEAST 2 INCHES OF RAIN (30-60%) THROUGH EARLY NEXT WEEK FROM
CENTRAL MINNESOTA THROUGH CENTRAL/NORTHERN WISCONSIN, BUT WE'LL
HAVE TO KEEP AN EYE ON WHETHER THIS AREA SHIFTS A BIT SOUTHWARD
INTO THE HIGHER INSTABILITY ENVIRONMENT. GIVEN MULTIPLE DAYS
(LATE FRIDAY THROUGH MON NIGHT/TUES) CONDITIONALLY FAVORABLE
FOR HEAVY RAINFALL, A FLOOD THREAT COULD INCREASE IF
THUNDERSTORMS FOCUS ALONG PREFERRED CORRIDORS DURING THIS TIME.
CONVECTIVE RAINFALL RATES ALONE MAY BE SUFFICIENT TO CAUSE
FLOOD CONCERNS EVEN OVER SHORTER TIME SCALES, GIVEN THE
ENVIRONMENTAL CONDITIONS. DESPITE THE OVERALL FAVORABLE PATTERN
FOR HEAVY RAIN, CONFIDENCE REMAINS LOW ON THE TIMING/PLACEMENT
OF STORMS GOING THROUGH THE WEEKEND, BUT IT CERTAINLY LOOKS TO
BE AN ACTIVE STRETCH OF WEATHER FROM THIS WEEKEND THROUGH EARLY
NEXT WEEK.
FRIDAY AND SATURDAY LOOK TO BE THE WARMEST DAY WITH HIGHS WELL INTO
THE 80S AND HEAT INDICES POTENTIALLY TOPPING 90 ACROSS PARTS OF
CENTRAL AND EAST-CENTRAL WISCONSIN ON SATURDAY WITH A VERY MUGGY
AIRMASS. HOWEVER, THE SPREAD IN FORECAST TEMPS INCREASES THIS
WEEKEND INTO EARLY NEXT WEEK DUE TO THE POTENTIAL IMPACTS FROM
CLOUDS/STORMS.
MID TO LATE NEXT WEEK: DRYING OUT
GLOBAL ENSEMBLES SHOW THE MID-LEVEL RIDGE AXIS RETROGRADING WESTWARD
TOWARDS THE FOUR CORNERS REGION LATER NEXT WEEK WITH A PERIOD OF
DRIER NORTHWEST FLOW AND SURFACE RIDGING EXPECTED. TEMPS SHOULD BE
NEAR SEASONAL AVERAGES.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1109 PM CDT THU AUG 14 2025
VFR CONDITIONS THROUGH THE TAF PERIOD, THOUGH THERE WILL BE
OPPORTUNITY FOR SOME SHOWERS AND STORMS. FIRST POTENTIAL WILL
BE EARLY IN THE OVERNIGHT, BUT THESE SHOULD MISS NORTH OF RHI. A
FEW SHOWERS MAY MAKE IT INTO CENTRAL WI TOWARD 12Z, BUT SEEMS THEY
MAY RUN OUT OF STEAM BY THAT TIME OR JUST END UP BEING SPRINKLES,
SO HAVE NOT INCLUDED. REMNANTS OF STORMS DEVELOPING OVER NORTHERN
MN CURRENTLY MAY GRAZE RHI 12Z-16Z AND HAVE INCLUDED A PROB30
GROUP TO COVER. NO TS MENTION NOW, BUT POSSIBLE THERE MAY BE A
RUMBLE OF THUNDER.
BETTER CHANCES FOR STORMS COMING INTO FOCUS FRIDAY EVENING OVER
CENTRAL AND NORTH-CENTRAL WI. ENOUGH CONFIDENCE TO NOW INCLUDE
PROB30 GROUPS FOR TS AT CWA/AUW/RHI. NO MENTION OF WIND GUSTS YET,
BUT COULD SEE THAT BEING ADDED IN LATER TAF ISSUANCES AS DAMAGING
WINDS AND TORRENTIAL RAIN WILL BE THE PRIMARY HAZARDS FROM
STRONGER STORMS. NOT ENOUGH CONFIDENCE YET TO INCLUDE FARTHER
EAST AT ATW/GRB/MTW, AT LEAST THROUGH END OF THE TAF PERIOD.
WINDS WILL REMAIN SOUTHERLY THROUGH FRIDAY EVENING, MOSTLY UNDER
10 KTS, THOUGH GUSTS OVER 15 KTS ARE POSSIBLE AT RHI LATE FRIDAY
MORNING THROUGH FRIDAY AFTERNOON.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....JM
AVIATION.......JLA
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