188
FXUS63 KGRR 091938
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
338 PM EDT SAT AUG 9 2025
KEY MESSAGES
- HEAT CONTINUES INTO MONDAY
- PERIODIC CHANCES FOR SHOWERS AND STORMS THROUGH TUESDAY
- SLIGHTLY COOLER/DRIER MID WEEK THEN ANOTHER WEEKEND WARMUP
DISCUSSION
ISSUED AT 338 PM EDT SAT AUG 9 2025
- HEAT CONTINUES INTO MONDAY
THE HEAT AND HUMIDITY WILL PERSIST THROUGH THE WEEKEND AND INTO
EARLY NEXT WEEK. HIGHS SUNDAY AND MONDAY WILL BE SIMILAR TO TODAY
WHICH MEANS WE SHOULD BE A FEW DEGREES EITHER SIDE OF 90 (AT LEAST
FOR THE SOUTHERN HALF OF THE FORECAST AREA, NEAR AND SOUTH OF
I-96). CLOUDS AND PRECIPITATION MAY KEEP CENTRAL LOWER A BIT
COOLER. HEAT INDEX VALUES WILL PUSH INTO THE MIDDLE 90S FOR A
GOOD PORTION OF THE AREA ON SUNDAY AND MONDAY. MOST OF THE AREA
WILL BE BACK INTO THE 80S FOR HEAT INDEX VALUES ON TUESDAY DUE TO
CLOUDS AND PRECIPITATION. SO, NO HEAT HEADLINES NEEDED GIVEN WE
WILL BE SHY OF THE 100 DEGREE HEAT INDEX MARK THE NEXT FEW DAYS.
- PERIODIC CHANCES FOR SHOWERS AND STORMS THROUGH TUESDAY
CHANCES FOR SHOWERS AND THUNDERSTORMS AND THUNDERSTORMS WILL
EXIST EACH FORECAST PERIOD FROM TONIGHT THROUGH TUESDAY NIGHT. THE
CHANCES IN ANY ONE PERIOD WILL NOT BE SIGNIFICANTLY HIGH, BUT WE
CANNOT RULE IT OUT THROUGH TUESDAY. ON THE SYNOPTIC SCALE WE WILL
SEE A COLD FRONT APPROACH (WASHING OUT AS IT MOVES OUR DIRECTION)
INTO SUNDAY NIGHT. SO, UP UNTIL THAT TIME WE WILL SEE CONVECTION
IN A DECAYING STATE TRYING TO MOVE IN TONIGHT, SUNDAY AND INTO
SUNDAY NIGHT. ALOFT WE WILL BE ALONG THE WESTERN EDGE OF AN UPPER
RIDGE WITH CONVECTIVE VORTS SLIDING NORTHEAST IN THE SOUTHWEST
FLOW. SREF POPS TELL THE STORY THE BEST WITH THE HIGHEST
LIKELIHOOD OF SHOWERS AND STORMS MOVING INTO OUR AREA BEING THE
NORTHWEST UP TOWARDS LUDINGTON OVERNIGHT TONIGHT, CENTRAL LOWER
MICHIGAN DURING THE DAY ON SUNDAY AND THE LAKESHORE SUNDAY NIGHT.
DEEP LAYER SHEAR IS ON THE WEAK SIDE AND CORRESPONDINGLY THE HREF
SHOWS ALMOST NO POTENTIAL FOR ROTATING UPDRAFTS IN OUR AREA
THROUGH SUNDAY NIGHT GIVEN THE LACK OF UPDRAFT HELICITY SWATHS.
SOME DECAYING LINEAR CONVECTION WILL BE OUR LIKELY MODE AND WE
WILL BE MONITORING ANYTHING MOVING OUR DIRECTION FOR INBOUND WIND
ON THE 88D'S.
BETTER CHANCES FOR SHOWERS AND STORMS WILL COME MONDAY INTO
TUESDAY WHEN A REINFORCING COLD FRONT DROPS IN FROM THE NORTHWEST
AHEAD OF AN UPPER SHORTWAVE TROUGH. THESE STORMS WILL HAVE MORE
SYNOPTIC SCALE SUPPORT AND THEREFORE WILL LIKELY BE BETTER
ORGANIZED WITH 30 KNOTS OF DEEP LAYER SHEAR. MUCH OF OUR CWA WILL
BE IN PLAY FOR STRONGER STORMS ON MONDAY AND THE EASTERN CWA ALONG
U.S. 127 ON TUESDAY.
- SLIGHTLY COOLER/DRIER MID WEEK THEN ANOTHER WEEKEND WARMUP
WE COOL A BIT MID WEEK AS 850MB TEMPERATURES BACK OFF INTO THE
MIDDLE TEENS C. WE SHOULD SEE HIGHS IN THE LOWER TO MIDDLE 80S IN
MOST AREAS. HEAT BUILDS BACK INTO THE AREA OVER THE UPCOMING
WEEKEND THROUGH WITH 850MB TEMPS REACHING +21C. WE WILL TO BE DRY
IN THE MIDDLE TO LATE WEEK WITH ANOTHER FRONT APPROACHING FROM THE
NORTHWEST NEXT SATURDAY.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 134 PM EDT SAT AUG 9 2025
VERY HIGH CONFIDENCE FOR VFR CONDITIONS THROUGH 00Z AT ALL
TERMINALS AND HIGH CONFIDENCE THROUGH 06Z FOR ALL TERMINALS EXCEPT
FOR MKG, WHICH HAS ABOUT A 20 PERCENT CHANCE OF A THUNDERSTORM
SHORTLY AFTER 00Z. WE TOYED WITH THE IDEA OF ADDING PROB30 TO MKG
FOR THE 00-02Z TIMEFRAME, BUT THERE REMAINS LIMITED CERTAINTY
REGARDING WHETHER CURRENT THUNDERSTORMS OVER WI WILL MAINTAIN
THEMSELVES AS THEY ENTER LAKE MICHIGAN LATE THIS AFTERNOON/EARLY
THIS EVENING.
WINDS AND GUSTS HAVE BEEN SOMEWHAT STRONGER THAN EXPECTED THIS
AFTERNOON, BUT STILL EXPECT THESE TO SUBSIDE AT THE INLAND
TERMINALS BY 22Z.
MARINE
ISSUED AT 338 PM EDT SAT AUG 9 2025
THE BEACH HAZARDS STATEMENT AND SMALL CRAFT ADVISORY STILL LOOK
GOOD IN TERMS OF AREA AND TIMING. CURRENTLY THE MUSKEGON BUOYS ARE
AROUND 3 FEET ON THE SOUTH END OF THE HEADLINES AND 4 FEET AT THE
LUDINGTON BUOYS ON THE NORTHERN END OF THE HEADLINES. FURTHER
SOUTH AT PORT SHELDON AND HOLLAND THE CONDITIONS ARE MORE AROUND 2
FEET, SO THINGS ARE WORKING OUT WELL. WE STILL FEEL THAT THE 11PM
ENDING IS A GOOD TIME AS THE WAVEWATCH3 IS SHOWING CONDITIONS
DAMPENING OUT BEFORE THAT TIME. SO, DANGEROUS CONDITIONS WILL
CONTINUE NORTH OF MUSKEGON THROUGH SUNSET.
OVERNIGHT WAVES WILL SUBSIDE INTO THE 1 TO 3 FOOT RANGE ACROSS ALL
FORECAST ZONES. ON SUNDAY, THERE WILL BE A BIT OF AN INCREASE IN
THE WIND ONCE AGAIN BUT WE FEEL CONDITIONS WILL REMAIN BELOW
ADVISORY/STATEMENT CRITERIA. 2-4 FOOTERS TO THE NORTH OF MUSKEGON
ON SUNDAY AND 1-3 TO THE SOUTH.
GRR WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT UNTIL 11 PM EDT THIS EVENING FOR MIZ037-
043-050.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LMZ847>849.
DISCUSSION...DUKE
AVIATION...TJT
MARINE...DUKE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page