914
FXUS63 KGRR 121752
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
152 PM EDT WED AUG 12 2026
KEY MESSAGES
- CHANCE FOR SCATTERED THUNDERSTORMS TODAY
- SATURDAY AND SUNDAY IS THE NEXT GOOD CHANCE FOR STORMS
- SEASONABLE TEMPERATURES EXPECTED
DISCUSSION
ISSUED AT 359 AM EDT WED AUG 12 2026
- CHANCE FOR SCATTERED THUNDERSTORMS TODAY
HIGH RESOLUTION MODELS ALL HAVE A SIGNAL FOR SCATTERED STORMS
TODAY AND THE SPC OUTLOOK AGREES WITH GENERAL THUNDER AND A
MARGINAL RISK ACROSS THE FORECAST AREA. LOOKING AT THE 24 HOUR MAX
REFLECTIVITY FROM THE HREF THERE ARE TWO MAIN ZONES FOR CONVECTION.
THE FIRST IS IN THE SPC MARGINAL RISK ACROSS CENTRAL LOWER
MICHIGAN. STORMS MAY BOTH DEVELOP THIS MORNING AND AGAIN THIS
AFTERNOON OVER CENTRAL LOWER, PEELING TO THE SOUTHEAST INTO THE
THUMB WITH TIME. THE SECOND AREA OF FOCUS IS REALLY JUST TO THE
SOUTH AND WEST OF THE AREA LIKE YESTERDAY. THE RAP IS SHOWING
1000-2000 J/KG OF MUCAPE AT MAX HEATING. STRONGER MID LEVEL WINDS
ARE NOTED OVER CENTRAL AND NORTHERN LOWER, SO IF THERE ARE CHANCES
FOR SEVERE WEATHER TODAY IT WILL LIKELY BE UP IN CENTRAL LOWER
WITH WIND BEING THE MAIN THREAT.
- SATURDAY AND SUNDAY IS THE NEXT GOOD CHANCE FOR STORMS
WE WILL LARGELY BE DRY AFTER THIS EVENING UNTIL WE GET TO SATURDAY
NIGHT AND SUNDAY WHEN OUR NEXT SYSTEM WILL BE WORKING THROUGH THE
STATE. A MID LEVEL SHORTWAVE LOOKS TO BE THE DRIVER OF THIS
CONVECTION AS IT TOPS THE CENTRAL PLAINS RIDGE AND MOVES THROUGH
THE GREAT LAKES. DEW POINTS SURGE INTO THE 70S WITH MUCAPE VALUES
IN EXCESS OF 2000 J/KG SO STRONGER STORMS ARE CERTAINLY POSSIBLE,
ESPECIALLY GIVEN MID LEVEL FLOW AROUND 40 KNOTS.
- SEASONABLE TEMPERATURES EXPECTED
NO MAJOR CHANGES IN TEMPERATURE ARE EXPECTED. HIGHS LOOK TO BE IN
THE 80S RIGHT THROUGH THE 7 DAY FORECAST.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 150 PM EDT WED AUG 12 2026
A SOMEWHAT COMPLEX AVIATION FORECAST FOR SOUTHWEST MICHIGAN. LOW
LEVEL MOISTURE ADVECTION INTO THE I-94 CORRIDOR /NORTH OF INDIANA
CONVECTION/ IS CONTINUING TO SUPPORT STUBBORN /IFR/ LOW CLOUDS
AND REDUCED VSBYS AT AZO/BTL/JXN. MODELS SUPPORT IMPROVING
CONDITIONS BY LATE AFTERNOON, BUT THIS PROCESS MAY BE SLOWED GIVEN
MID/UPPER CLOUDS AND LACK OF DRIER AIR NEAR SURFACE. TAFS REFLECT
IMPROVING CONDITIONS TO VFR AT AZO/BTL/JXN AFTER 20Z, BUT THIS
COULD EASILY BE DELAYED. IN FACT, WILL NEED TO MONITOR SOME OF
THESE LOWER CLOUDS POSSIBLY REACHING LAN NEXT 1-2 HR.
ELSEWHERE, INCLUDING MKG/GRR/LAN, A SMATTERING OF CU/SC AND SCT-
BKN AC/CI IS BEING OBSERVED, BUT VFR CONDITIONS PREVAIL. EXPECT
LOW CLOUDS AND FOG TO REFORM AFTER 05Z AND CONTINUE THROUGH
DAYBREAK. THEN, VFR WEATHER WILL RETURN AFTER ROUGHLY 13Z WITH
MAINLY HIGH CLOUDS EXPECTED.
WINDS WILL REMAIN LIGHT AND VARIABLE THROUGH TONIGHT, THEN BECOME
E/SE UNDER 10KT ON THURSDAY.
MARINE
ISSUED AT 359 AM EDT WED AUG 12 2026
LIMITED CONCERNS IN THE NEXT FEW DAYS IN TERMS OF WINDS AND WAVES.
WE ARE IN A FAIRLY SLACK PRESSURE GRADIENT THROUGH THE REMAINDER
OF THE WEEK SO WAVES SHOULD BE 2 FEET OR LESS. OTHERWISE, THE TWO
MAIN CONCERNS ARE FOG AND THUNDERSTORMS. THUNDERSTORMS ARE
POSSIBLE TODAY OVER LAKE MICHIGAN SO MARINERS AND BEACH GOERS WILL
NEED TO KEEP THAT IN MIND AS WINDS AND WAVES ARE USUALLY HIGHER
IN AND NEAR STORMS. FOG WILL REMAIN A THREAT OVER THE WATER UNTIL
WE CAN BRING IN DRIER DEW POINTS. THAT DOES NOT REALLY HAPPEN THIS
WEEK SO THE THREAT OF FOG WILL CONTINUE.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...DUKE
AVIATION...SMITH
MARINE...DUKE
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