948
FXUS63 KGRR 031759
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
159 PM EDT THU SEP 3 2026
KEY MESSAGES
- SPC SLIGHT RISK FOR SEVERE WEATHER OVER MUCH OF THE AREA TODAY
- THUNDERSTORM CHANCES MAY LINGER INTO FRIDAY
- DRY WEATHER EXPECTED OVER THE WEEKEND
UPDATE
ISSUED AT 1052 AM EDT THU SEP 3 2026
A FAIRLY ACTIVE MIDDAY INTO AFTERNOON PERIOD IS LIKELY WITH
ADDITIONAL THUNDERSTORMS DEVELOPING ACROSS WISCONSIN AND
CENTRAL/NORTHERN LAKE MICHIGAN, MOVING EAST PER THE 850-300MB
MEAN FLOW. AN MCV IS NOTED SOUTHEAST OF MADISON. SPC MESOANALYSIS
INDICATES MORNING CIN SHOULD ERODE ESPECIALLY AWAY FROM THE
LAKESHORE REGION AROUND 16Z OR SO, WITH SBCAPE VALUES OF 2000-3000
J/KG AND DCAPE VALUES AROUND 1000 J/KG AHEAD OF BOTH THE MCV AND
DEVELOPING CONVECTION NEAR GREEN BAY. EITHER ONE OF THESE AREAS
MAY GET BETTER ORGANIZED AFTER MOVING PAST THE LAKE IN THE 16Z-18Z
TIME FRAME. 12Z CAM MAX CONVECTIVE GUSTS INDICATE A SIGNAL FOR
POTENTIAL 60+ MPH GUSTS ESPECIALLY FROM 18Z ONWARD EAST OF US
131. GIVEN SUBSTANTIAL INSTABILITY AND ALSO THE PRESENT SPC LARGE
HAIL PARAMETERS OVERHEAD, QUARTER SIZE HAIL OR LARGER IS ALSO
POSSIBLE.
DISCUSSION
ISSUED AT 400 AM EDT THU SEP 3 2026
- SPC SLIGHT RISK FOR SEVERE WEATHER OVER MUCH OF THE AREA TODAY
THE PATTERN CONTINUES TO SUPPORT THE THREAT OF THUNDERSTORMS OVER
THE NEXT 24 HOURS, INCLUDING BOTH TODAY AND TONIGHT. AT THE
SURFACE WE HAVE ESSENTIALLY A STATIONARY BOUNDARY STRETCHING FROM
EAST/WEST NEAR THE I-96 CORRIDOR. DEW POINTS TO THE NORTH ARE IN
THE 60S AND ARE IN THE 70S TO THE SOUTH. MUCAPE VALUES ARE
STRATIFIED CORRESPONDINGLY WITH 2,000 J/KG IN PLACE TO THE SOUTH
AND 500-1,000 TO THE NORTH. THE UPPER FLOW PATTERN WILL LIKELY
BRING IN CONVECTIVELY INDUCED VORTICITY MAXIMA FROM THE WEST TODAY
(THE IA/MN CONVECTION). TONIGHT MODELS SUGGEST A NW TO SE MOVING
SHORTWAVE THAT MAY BRING ADDITIONAL STORMS TO THE AREA. THE BEST
LLJ ORIENTATION AND MAGNITUDE OCCUR EARLY THIS MORNING THROUGH
SUNRISE AND AGAIN TONIGHT COMING UP. CONFIDENCE IN THE EVOLUTION
REMAINS ON THE LOWER SIDE TODAY/TONIGHT, BUT WE DO FEEL WE WILL
LIKELY SEE ADDITIONAL STORMS THIS MORNING, ADDITIONAL CHANCES THIS
AFTERNOON, FOLLOWED BY MORE STORMS TONIGHT. WIND APPEARS TO BE THE
MAIN THREAT PER MACHINE LEARNING DATA LIKE NADOCAST WHICH IS
SUPPORTED BY THE SPC OUTLOOKS. EARLY AFTERNOON SOUNDINGS VIA THE
HRRR IN OTTAWA COUNTY ARE INDICATING 1,100 J/KG OF DCAPE WHICH
SHOWS THE POTENTIAL FOR DAMAGING WINDS.
PWAT VALUES CONTINUE TO BE HIGH BOTH TODAY AND TONIGHT WITH 2.0
VALUES BOTH FORECAST PERIODS. STORMS HAVE THE POTENTIAL TO BE
MOVING QUICKLY, BUT RAINFALL RATES WILL LIKELY BE HIGH GIVEN DEEP
SUMMER VALUES OF PWAT. IF STORMS CAN TRAIN OVER CERTAIN AREAS OR
IF MOTION IS SLOWER THAN ANTICIPATED HYDRO CONCERNS WILL INCREASE
(LOCALIZED SHORT TERM FLOODING).
- THUNDERSTORM CHANCES MAY LINGER INTO FRIDAY
MODELS INDICATE THE POTENTIAL FOR SOME STORMS LINGERING INTO
FRIDAY MORNING IN A NORTHWEST FLOW ALOFT JUST DOWNSTREAM OF THE
PLAINS UPPER RIDGE. SPC HAS A MARGINAL THREAT FOR SEVERE WEATHER
IN OUR FAR SOUTHWEST WHICH MAKES SENSE GIVEN THE MOISTURE WILL BE
POOLED IN THIS AREA AS THE FRONT LIKELY SAGS TO THE SOUTHWEST.
- DRY WEATHER EXPECTED OVER THE WEEKEND
THE PATTERNS LOOKS TO TRY AND DRY OUT THIS WEEKEND AS HIGH
PRESSURE BUILDS IN FROM THE NORTH AND NORTHEAST. BUFKIT MOISTURE
OVERVIEWS THIS WEEKEND ARE STARKLY DRIER THAN WHAT WE HAVE SEEN
ALL THIS WEEK.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 153 PM EDT THU SEP 3 2026
RADAR SHOWS ABUNDANT CONVECTION OVERSPREADING LOWER MI AND IT
MIGHT NOT BE THE ONLY ROUND WE SEE DURING THE PERIOD. MOST OF THE
TAF PERIODS HAVE A PROB30 FOR STORMS SINCE WE NEED TO ACCOUNT FOR
THE CURRENT CONVECTION AND ANOTHER ROUND LATER TONIGHT THAT
SEVERAL MODELS CONTINUE TO SHOW. A FEW OF THE STORMS COULD BE
STRONG TO SEVERE THIS AFTERNOON AND OVERNIGHT. THERE MAY BE A LULL
IN THE CONVECTION DURING THIS EVENING.
OUTSIDE OF THE STORMS, EXPECT MVFR FOG OVERNIGHT DUE TO HIGH
DEWPOINTS AND ABUNDANT MOISTURE FROM RECENT RAIN.
MARINE
ISSUED AT 400 AM EDT THU SEP 3 2026
THE SURFACE PATTERN REMAINS FAIRLY BENIGN THE NEXT FEW DAYS WITH
LIGHTER SYNOPTIC SCALE WINDS EXPECTED. WINDS SHOULD REMAIN AT OR
BELOW THE 5-15 KNOT RANGE WHICH WILL RESULT IN WAVES OF 2 FEET OR
LESS THROUGH SATURDAY. NO ADVISORY LEVEL WAVE EVENTS ARE EXPECTED.
THE ONE ITEM TO KEEP AN EYE ON THOUGH IS THE THREAT OF
THUNDERSTORMS AND STRONGER WINDS ASSOCIATED WITH THEM. WE WILL BE
IN A PATTERN CONDUCIVE FOR STORMS AND WIND TODAY. WINDS AND WAVES
CAN OBVIOUSLY BE HIGHER IN AND NEAR THUNDERSTORMS AND MARINERS
WILL NEED TO REMAIN ALERT TO THIS THREAT.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
UPDATE...HOVING
DISCUSSION...DUKE
AVIATION...04
MARINE...DUKE
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