633
FXUS63 KGRR 282208
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
608 PM EDT SUN JUN 28 2026
KEY MESSAGES
- THREAT OF STRONG TO SEVERE STORMS LATE TONIGHT/MONDAY AM
- HEAT WAVE BEGINS MONDAY
UPDATE
ISSUED AT 608 PM EDT SUN JUN 28 2026
THUNDERSTORMS ACROSS CENTRAL EASTERN WISCONSIN HAVE PERSISTED PAST
COUPLE HOURS IN AN AREA OF DEEP WARM ADVECTION NEAR AND NEAR THE
SURFACE WARM FRONT. ADDED POPS FOR THE WESTERN ZONES AS
CONVECTION MOVES SOUTHEAST OUT OF WISCONSIN AND ACROSS THE LAKE
THE NEXT FEW HOURS. THE FV3 SEEMS TO HAVE A HANDLE ON THE
PREVIOUS AND CURRENT CONVECTION AND WAS FOLLOWED AS IT TAKES THESE
STORMS EASR-SOUTHEAST THIS EVENING.
WAKE LOW WINDS NOTED OVER SOUTHERN WISCONSIN AND NORTHERN ILLINOIS
GUSTING OVER 40 MPH. THE ARE EXPECTED TO WEAKEN AS THEY MOVE
SOUTHEAST ACROSS LAKE MICHIGAN, BUT SOME SQUALLS AND BRIEF GALES
ARE POSSIBLE ACROSS THE SOUTHERN MARINE ZONES AND WE HAVE ISSUED A
MARINE WEATHER STATEMENT.
DISCUSSION
ISSUED AT 218 PM EDT SUN JUN 28 2026
- THREAT OF STRONG TO SEVERE STORMS LATE TONIGHT/MONDAY AM
SEVERAL SHORT RANGE MODELS, SUCH AS THE HREF, NAMNEST, RRFS, AND
SOME RUNS OF THE HRRR SHOW THE DEVELOPMENT OF AN MCS OVER
NORTHEAST WISCONSIN TONIGHT MOVING EAST AND THEN MOVING SOUTH
ALONG THE LAKE SHORE FOLLOWING THE THICKNESS GRADIENT. MUCAPE
INCREASES TO 1500 J/K TOWARD 12Z ALONG THE LAKE SHORE AND SHEAR
VALUES ARE PROGD NEAR 40KTS. SO THE POTENTIAL EXISTS FOR A FEW
STRONG TO SEVERE STORMS LATE TONIGHT AND EARLY MONDAY MORNING
BEFORE THE STORMS DISSIPATE.
- HEAT WAVE BEGINS MONDAY
A BUILDING UPPER RIDGE OVER THE GREAT LAKES WILL RESULT IN
OPPRESSIVE HEAT DEVELOPING TOMORROW AND CONTINUE THROUGH MOST OF
THE WEEK. H8 TEMPS INCREASE FROM 18C MONDAY TO 24C BY TUESDAY
AFTERNOON. HIGH TEMPERATURES WILL BE IN THE 90S THROUGH FRIDAY.
HIGHS AROUND 100 ARE POSSIBLE WEDNESDAY AND THURSDAY ACROSS THE
SOUTHEAST CWA. HEAT INDICES WILL TOP 105 IN MAY LOCATIONS THANKS
TO DEWPOINTS CLIMBING INTO THE 70S. PERHAPS THE WORST PART WILL BE
THE LACK OF RELIEF. LOW TEMPERATURES DURING THE WEEK WON'T GET
BELOW 75 IN MANY LOCATIONS.
AS THE WEEK PROGRESSES, THERE WILL BE SHORT WAVES THAT RIDE UP THE
WESTERN SIDE OF THE RIDGE AND TRY TO FLATTEN THE RIDGE ACROSS
NORTHERN LOWER...MOST LIKELY THURSDAY NIGHT. THIS MAY RESULT IN
SOME CONVECTION OVER THE CWA, SO WE'LL KEEP AN EYE ON THAT.
THROUGHOUT THIS UPCOMING HEAT WAVE, MAKE SURE TO CHECK ON THE
ELDERLY AND ENSURE YOUR PETS HAVE PLENTY OF CLEAN FRESH WATER.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 130 PM EDT SUN JUN 28 2026
SATELLITE SHOWS DIURNAL CU DEVELOPMENT BETWEEN 3-4KFT WHICH WILL
LAST THROUGH THE EVENING. THEN WE SEE CIGS LOWER TO AROUND 5KFT
THROUGH THE NIGHT AS A SYSTEM APPROACHES FROM THE WEST. THE MAIN
POTENTIAL IMPACT, AND SOURCE OF UNCERTAINTY, IS THE POTENTIAL FOR
A THUNDERSTORM COMPLEX TO CLIP GRR/MKG LATE TONIGHT OR MONDAY
MORNING. SHORT RANGE MODEL GUIDANCE IS NOT IN STRONG AGREEMENT ON
WHERE OR WHEN EXACTLY STORMS WILL TRACK SO HAVE KEPT THE PROB30S
INHERITED FROM THE PREVIOUS FORECASTER. OUTSIDE OF WINDS IN
THUNDERSTORMS, LOOK FOR SOUTHEAST WINDS TO 10 KNOTS TODAY EXCEPT
FOR A WESTERLY LAKE BREEZE AT MKG. SOUTH TO SOUTHEAST WINDS ARE
EXPECTED AGAIN MONDAY WITH GUSTS TO 20 KNOTS AT MKG.
MARINE
ISSUED AT 218 PM EDT SUN JUN 28 2026
SOUTH WINDS WILL INCREASE TONIGHT AND CONTINUE THROUGH MONDAY AND
WAVES WILL RESPOND BY BUILDING TO 3-5 FT. WE'VE ISSUED A SMALL
CRAFT ADVISORY AND CORRESPONDING BEACH HAZARDS STATEMENT FROM 06Z
TONIGHT THROUGH TUESDAY. ADDITIONALLY, THUNDERSTORMS MAY SPREAD
SOUTH ALONG THE LAKE SHORE LATE TONIGHT RESULTING IN HAZARDOUS
MARINE CONDITIONS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT FROM 2 AM EDT MONDAY THROUGH TUESDAY
EVENING FOR MIZ037-043-050-056.
EXTREME HEAT WARNING FROM 2 PM MONDAY TO 8 PM EDT THURSDAY FOR
MIZ037>040-043>046-050>052-056>059-064>067-071>074.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM MONDAY TO 8 PM EDT TUESDAY FOR
LMZ846>849.
UPDATE...OSTUNO
DISCUSSION...04
AVIATION...THOMAS
MARINE...04
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