668
FXUS63 KGRR 120617
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
217 AM EDT WED AUG 12 2026
KEY MESSAGES
- SHOWERS AND STORMS MOVING TO THE SOUTH; PATCHY FOG OVERNIGHT
- CHANCES FOR STORMS TOMORROW
- NEXT CHANCE FOR SHOWERS/STORMS OVER THE WEEKEND
DISCUSSION
ISSUED AT 303 PM EDT TUE AUG 11 2026
- SHOWERS AND STORMS MOVING TO THE SOUTH; PATCHY FOG OVERNIGHT
THE QUASISTATIONARY BOUNDARY CONTINUES TO SAG SOUTHWARD AND WILL
PUSH ANY SHOWERS/STORMS IN THAT DIRECTION. THERE HAS BEEN SOME
LIGHT RAIN ALONG THE I 94 CORRIDOR, WITH THE ANVIL FROM THE
THUNDERSTORMS THROUGH SOUTHERN MICHIGAN BRINGING SOME RUMBLES OF
THUNDER AND VICINITY LIGHTING TO THAT REGION. HOWEVER, THE STORMS
THEMSELVES CONTINUE THEIR SOUTHWARD TREK TOWARD THE SOUTHEAST.
LIGHT WINDS, A MOIST SURFACE LAYER AND RECENT RAINFALL IS A
RECIPE FOR PATCHY FOG OVERNIGHT INTO WEDNESDAY MORNING. EXPECT
THIS FOG TO BE DENSE AT TIMES AND WILL LINGER THROUGH THE MORNING
COMMUTE.
- CHANCES FOR STORMS TOMORROW
THOUGH THERE IS A SIGNAL FOR DECENT CAPE VALUES FROM THE SFC
MOISTURE AND DAYTIME TEMPERATURES INTO THE 80S, THE ATMOSPHERE IS
FAIRLY STABLE, ESPECIALLY SINCE THE BOUNDARY REMAINS TO THE SOUTH.
LATEST HREF DOES SHOW THE POTENTIAL FOR A WEAK MID LEVEL TROUGH
AND SOME SHEAR THROUGH NORTHERN LOWER MICHIGAN IN THE AFTERNOON.
THAT COULD TAKE ADVANTAGE OF THE 1K J/KG OF CAPE WEDNESDAY
AFTERNOON. FOR THOSE REASONS, SPC HAS A RIBBON OF MARGINAL RISK OF
SEVERE STORMS THROUGH THE CENTRAL AND NORTHERN HALF OF LOWER MI
TOMORROW AFTERNOON AND EVENING.
- NEXT CHANCE FOR SHOWERS/STORMS OVER THE WEEKEND
THE LARGE UPPER LEVEL LOW OVER NORTHERN CANADA CONTINUES TO SEND
WAVES THROUGH MICHIGAN THROUGH THE WEEK. HOWEVER, WE REMAIN
FAIRLY STABLE THROUGH THE LATTER HALF OF THE WEEK WITH
TEMPERATURES AT, TO BELOW NORMAL INTO THE WEEKEND. A LARGE UPPER
LEVEL LOW WILL MOVE INTO THE THE GREAT LAKES REGION THROUGH THE
AREA MID TO LATE WEEKEND WITH CHANCE FOR RAIN INTO SUNDAY.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 217 AM EDT WED AUG 12 2026
THE BEAT GOES ON IN TERMS OF AVIATION WEATHER CONCERNS TODAY, THEY
ARE THE SAME AS THEY HAVE BEEN THE LAST FEW DAYS, FOG AND STORMS.
VARIABLE CONDITIONS ARE IN PLACE TO START THE TAF PERIOD ONCE
AGAIN WITH LIFR TO VFR WEATHER OCCURRING IN CLOSE PROXIMITY. IN A
LIGHT WIND / HIGH MOISTURE SETUP THIS IS TO BE EXPECTED AS
RADIATIONAL COOLING ALLOWS FOR RAPID FOG FORMATION AND
DISSIPATION. WE DO EXPECT A DOWNWARD TREND THE REMAINDER OF THE
NIGHT HOWEVER WITH FAIRLY WIDESPREAD IFR AND LIFR FORECAST BY 11Z.
THE FOG AND STRATUS SHOULD LIFT QUICKLY ONCE AGAIN TODAY WITH VFR
WEATHER RETURNING BY 15Z-16Z.
STORMS ARE ONCE AGAIN IN THE FORECAST TODAY, BUT THE SIGNAL IS NOT
AS STRONG FOR CERTAIN THUNDERSTORM DEVELOPMENT. WE FEEL MANY OF
THE TAF SITES MAY STAY STORM FREE TODAY WITH THE BULK OF THE
ACTIVITY STAYING TO THE NORTH, EAST AND SOUTH OF THE TAF SITES. A
ZONE OF STORMS ARE EXPECTED FROM PORTIONS OF CENTRAL LOWER
MICHIGAN INTO THE THUMB TODAY WITH ANOTHER ZONE SWEEPING THE MI/IN
BORDER ONCE AGAIN. THEREFORE, WE CURRENTLY HAVE DRY TAFS GOING,
BUT KNOW GIVEN A SCATTERED NATURE TO THE STORMS IT IS NOT OUT OF
THE REALM OF POSSIBILITIES TO SEE SOME ACTIVITY TODAY. THE BETTER
BET IS FOR DRY THOUGH.
MARINE
ISSUED AT 312 PM EDT TUE AUG 11 2026
SHOWERS AND STORMS WILL MOVE TO THE SOUTH THIS AFTERNOON AND
EVENING. A TYPICAL MID SUMMER WEATHER PATTERN WILL CONTINUE THE
NEXT FEW DAYS. LIGHT WINDS WILL CONTINUE. EXPECT SUNSHINE AND
SOME OF OUR WARMEST WATER TEMPERATURES. WINDS AND WAVES WILL
REMAIN FAIRLY LIGHT THROUGH TOMORROW.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...CERU
AVIATION...DUKE
MARINE...CERU
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