693
FXUS63 KGRR 120743
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
343 AM EDT SAT JUL 12 2025
KEY MESSAGES
- SEVERE WEATHER CHANCES THIS AFTERNOON
- SHOWERS AND THUNDERSTORMS RETURN MID-WEEK
DISCUSSION
ISSUED AT 343 AM EDT SAT JUL 12 2025
- SEVERE WEATHER CHANCES THIS AFTERNOON
SHORTWAVE TROUGH AXIS GOES NEGATIVE TILT AS IT SWINGS THROUGH
TODAY WITH CONDITIONAL SEVERE THREAT ACROSS THE EASTERN ZONES THIS
AFTERNOON. MAIN THREAT WILL BE ISOLATED DOWNBURSTS WITH DEEP LAYER
SHEAR ONCE AGAIN A LIMITING FACTOR FOR PERSISTENT, ORGANIZED
CONVECTION, DESPITE 1500-2000 J/KG CAPE ACROSS THE AREA FROM LAN
TO JXN. SEVERE THREAT WINDS DOWN IN THE LATE AFTERNOON AND EARLY
EVENING AS STORMS SHIFT EAST.
- SHOWERS AND THUNDERSTORMS RETURN MID-WEEK
ZONAL FLOW WITH WEAK SFC RIDGING BRINGS FAIR WEATHER FOR SUNDAY
THROUGH TUESDAY THEN RAIN CHANCES RETURNS FOR MID-WEEK WITH THE
APPROACH OF A WEAK SHORTWAVE TROUGH. SHOWERS AND STORMS BECOME
MORE WIDESPREAD ON THURSDAY AS A COLD FRONT MOVES THROUGH. SEVERE
WEATHER THREAT ALSO INCREASES AS FORECAST DEEP LAYER SHEAR IS
PROGGED TO BE OVER 30 KNOTS ALONG WITH SUFFICIENT INSTABILITY FOR
ORGANIZED STORMS.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 130 AM EDT SAT JUL 12 2025
SCATTERED THUNDERSTORMS AND MVFR CONDITIONS WILL BE ACROSS LAKE
MICHIGAN AND NEAR MKG THROUGH ABOUT 08Z BUT CHANCES OF THUNDER IN
OTHER AREAS OF WESTERN LOWER MICHIGAN ARE LOW OVERNIGHT. SOME
LIGHT FOG COULD ALSO BRING PATCHY MVFR CONDITIONS THROUGH SUNRISE.
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO FLARE UP SATURDAY
AFTERNOON OVER ROUGHLY THE EASTERN HALF OF LOWER MICHIGAN WITH
SOME ISOLATED IFR CONDITIONS IN HEAVY RAIN ALONG WITH WINDS
GUSTING OVER 30 KNOTS AND SMALL HALL IN STRONGER STORMS.
MARINE
ISSUED AT 343 AM EDT SAT JUL 12 2025
SCATTERED THUNDERSTORMS TODAY COULD BRING WIND GUSTS OVER 30
KNOTS OTHERWISE WINDS SHOULD BE BELOW 25 KNOTS THROUGH THE WEEKEND
AND INTO EARLY NEXT WEEK.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...OSTUNO
AVIATION...OSTUNO
MARINE...OSTUNO
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