417
FXUS63 KGRR 121806
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
206 PM 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 /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 204 PM EDT SAT JUL 12 2025
HAVE REMOVED ANY MENTION OF STORMS FROM THE TAF'S AS THE FRONTAL
BOUNDARY HAS MOVED TO THE EAST. THERE IS STILL A SMALL CHANCE SOME
SHOWERS AND STORMS FORM LATER THIS EVENING BUT IT SHOULD BE NORTH
OF ALL THE TAF SITES. ONLY MKG HAS ANY CHANCE AND THAT WOULD
MAINLY BEEN MVFR FROM SHOWERS. OTHERWISE VFR WILL DOMINATE THE
FORECAST WITH GUSTY WINDS DECREASING EARLY THIS EVENING AND
BECOMING CALM AFTER SUNSET.
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...AIR QUALITY ALERT FROM MIDNIGHT TONIGHT TO NOON EDT MONDAY FOR
MIZ037>040-043>046-050>052-056>059-064>067-071>074.
MARINE...NONE.
DISCUSSION...OSTUNO
AVIATION...CERU
MARINE...OSTUNO
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