734
FXUS63 KGRR 151756
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
156 PM EDT FRI AUG 15 2025
KEY MESSAGES
- ROUNDS OF SHOWERS AND STORMS FROM SATURDAY THROUGH TUESDAY
- QUIET WEATHER MID TO LATE NEXT WEEK
- WARM TODAY AND SATURDAY
DISCUSSION
ISSUED AT 348 AM EDT FRI AUG 15 2025
- ROUNDS OF SHOWERS AND STORMS FROM SATURDAY THROUGH TUESDAY
WE MAY SEE STORMS INTO THE FORECAST AREA AS EARLY AS TONIGHT AS
CONVECTION TRIES TO ROLL EAST OUT OF WISCONSIN CROSSING THE LAKE
OVERNIGHT. BETTER CHANCES WILL EXIST FROM SATURDAY AND THEN
CONTINUING EACH FORECAST PERIOD OUT THROUGH TUESDAY. A COLD FRONT
WILL BE DROPPING SOUTH THROUGH THE AREA ON SATURDAY, SETTING UP AS
A WARM FRONT JUST SOUTH OF US SUNDAY INTO MONDAY BEFORE FINALLY
SLIDING SOUTH OF THE REGION ON TUESDAY.
PLENTY OF INSTABILITY WILL BE IN PLACE DURING THIS 4 DAY PERIOD
WITH UPPER 60S TO LOWER 70S DEW POINTS IN THE FORECAST AREA OR
NEARBY. MUCAPE VALUES WILL PEAK DURING THE DIURNAL PEAK EACH DAY
AND WILL LIKELY ECLIPSE 2,000 J/KG. DEEP LAYER SHEAR OVERALL IS
FAIRLY MODEST, BUT DOES INCREASE AT TIMES AS SURGES OF CONVECTION
MOVE THROUGH THE AREA. IT APPEARS SATURDAY AND THEN AGAIN MONDAY
MAY BE THE FAVORED PERIODS FOR SHOWERS AND STORMS ASSOCIATED WITH
CONVECTIVELY DRIVEN SHORTWAVES. CANNOT RULE OUT SOME ISOLATED
REPORTS OF SEVERE WEATHER, BUT WIDESPREAD SEVERE IS NOT EXPECTED.
WE ARE IN GENERAL THUNDER VIA SPC FOR TONIGHT AND ON SUNDAY. A
MARGINAL RISK STANDS FOR SATURDAY AND AGREE WITH ALL THREE
OUTLOOKS FOR OUR AREA FROM FRI-SUN.
PROBABLY THE BIGGEST THREAT FROM STORMS IN THE COMING DAYS WILL BE
LOCALLY HEAVY/TORRENTIAL RAIN. PWAT VALUES ARE VERY HIGH THROUGH
THE PERIOD, TOUCHING 2 INCHES IN ALMOST EVERY FORECAST PERIOD. THE
PEAK VALUES OCCUR MONDAY NIGHT WHEN WE APPROACH 2.25 INCHES.
THUNDERSTORM MOVEMENT MUCH OF THE TIME LOOKS TO BE SLOW. GIVEN THE
RAIN RATES AND SLOW MOVING STORMS LOCALIZED FLOODING IS A CONCERN.
- QUIET WEATHER MID TO LATE NEXT WEEK
QUIET WEATHER SETTLES IN BEHIND MULTIPLE DAYS OF STORMS FOR
WEDNESDAY THROUGH FRIDAY. HIGH PRESSURE SHOULD KEEP US DRY DURING
THIS TIME FRAME. TEMPERATURES COOL BACK TOWARDS NORMAL ONCE AGAIN
WITH HIGHS BETWEEN 80 AND 85.
- WARM TODAY AND SATURDAY
WE WILL BE WARM TODAY AND SATURDAY AS 850MB TEMPERATURES SURGE TO
+18C TO +19C TODAY AND +19C TO +20C ON SATURDAY. THIS SHOULD
RESULT IN HIGHS AROUND 90 BOTH TODAY AND SATURDAY. SATURDAY MAY
BE AFFECTED BY CLOUDS AND SHOWERS/STORMS HOWEVER SO WE WILL BE
WATCHING CONVECTIVE TRENDS AND ADJUSTING TEMPERATURES ACCORDINGLY.
HEAT INDEX VALUES WILL RISE WELL INTO THE 90S ON SATURDAY FROM
I-96 TO THE SOUTH AS THE DEW POINTS BUILD IN ONCE AGAIN.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 121 PM EDT FRI AUG 15 2025
VFR WILL DOMINATE THE FORECAST OVERNIGHT INTO TOMORROW. THERE IS
A CHANCE FOR LIGHT FOG EARLY TOMORROW. HOWEVER ONLY HAVE IT
SLIGHTLY AFFECTING JXN FOR A FEW HOURS BETWEEN 09 TO 12Z. THERE
WILL BE AN INCREASED RISK TOMORROW FOR SHOWERS AND PERHAPS SOME
AFTERNOON STORMS. HAVE LEFT OUT STORMS FROM THE TAFS FOR NOW AND
ONLY HAVE VCSH AT MKG AT THE MOMENT. THERE WILL BE AN INCREASED
RISK AFTER 15Z AND ESPECIALLY AFTER 18Z SATURDAY.
MARINE
ISSUED AT 155 PM EDT FRI AUG 15 2025
LIGHT SOUTHERLY FLOW WILL CONTINUE THROUGH TODAY INTO TOMORROW
WITH NO IMPACTS EXPECTED FOR THE LAKESHORE TODAY.
HOWEVER, THERE IS A CHANCE FOR SEVERAL ROUNDS OF SHOWERS AND
STORMS TOMORROW. SHOWERS AND STORMS SHOULD BEGIN LATE MORNING/EARLY
AFTERNOON WITH HAZARDOUS WINDS/WAVES IN AND AROUND STORMS.
SHOWERS AND STORMS WILL REMAIN POSSIBLE INTO SATURDAY NIGHT.
NORTHERLY FLOW WILL BUILD IN BEHIND THE FRONT SUNDAY. HOWEVER THIS
WILL BRING THE POTENTIAL FOR HIGHER WINDS AND WAVES. THERE
REMAINS QUESTION ON TIMEFRAME BUT SUNDAY AFTERNOON AND EVENING
COULD SEE WINDS/WAVES/CURRENTS REACH ADVISORY CRITERIA.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...04
AVIATION...CERU
MARINE...CERU
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