776
FXUS63 KGRR 040555
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
155 AM EDT SAT JUL 4 2026
KEY MESSAGES
- SEVERE THUNDERSTORM THREAT TODAY INTO TONIGHT
- SCATTERED THUNDERSTORMS POSSIBLE THIS WEEKEND
DISCUSSION
ISSUED AT 246 PM EDT FRI JUL 3 2026
- SEVERE THUNDERSTORM THREAT TODAY INTO TONIGHT
THIS MORNING'S CAMS HAVE BEEN OFFERING THE STRONGEST SIGNAL I HAVE
SEEN YET THIS WEEK FOR DEVELOPING CONVECTION THIS AFTERNOON AMID A
DESTABILIZING ATMOSPHERE IN OUR CWA (OTHER THAN THE SIGNAL THEY
HAD FOR US-10 AND NORTH STORMS ON WEDNESDAY). DESPITE THE MAJORITY
OF CAMS STRUGGLING TO INITIALIZE AND MAINTAIN THE NORTHERN
ILLINOIS CONVECTION, MOST ENDED UP EVENTUALLY DEVELOPING EITHER
SCATTERED CONVECTION OR A LOOSELY ORGANIZED LINE OF STORMS WITH A
SEVERE WIND THREAT ANYWAY (ALBEIT MODELED STORMS ARRIVING LATER
THAN REALITY). IT IS LIKELY THAT THE STORMS CURRENTLY OVER LAKE
MICHIGAN WILL BE TODAY'S PRIMARY THREAT, FOLLOWED BY A LULL IN ITS
WAKE IN THE EVENING, THEN PERHAPS A SECONDARY DEVELOPMENT OF
SCATTERED STORMS LATER THIS EVENING OR OVERNIGHT.
FOR THIS AFTERNOON, CONCERN IS FOR DESTABILIZATION OCCURING NEAR AND
SOUTH OF I-96 AS INCREASING CUMULUS FIELD IS SEEN DEVELOPING.
DOWNDRAFT CAPE, AS HAS BEEN THE CASE THIS WEEK, IS SUBSTANTIAL AT
1000-1200 J/KG. DEEP LAYER SHEAR IS NOT GREAT, BUT WIND SHEAR 0-3 KM
IS MARGINALLY SUPPORTIVE FOR A WIND-DRIVEN QLCS AT 25 KNOTS, PERHAPS
COULD ASSIST THE DEVELOPMENT OF MESOVORTS ALONG THE LINE WHICH WOULD
ENHANCE WIND DAMAGE THREAT IN NARROWER CORRIDORS (TORNADO THREAT IS
LOW BUT "GUSTNADOES" MAY INSTEAD BE THE MODE).
- SCATTERED THUNDERSTORMS POSSIBLE THIS WEEKEND
WHILE SOME UNCERTAINTY REMAINS IN THE DETAILS, SCATTERED
THUNDERSTORMS WITH AN ISOLATED GUSTY WIND THREAT REMAIN FAVORED
FOR PARTS OF THE DAY AND EVENING SATURDAY AND SUNDAY. A DEEPENING
UPPER LEVEL TROUGH OVER THE GREAT LAKES THIS WEEKEND WILL MAINTAIN
INSTABILITY AND A COUPLE EMBEDDED SHORTWAVES WOULD PROVIDE ADDED
LIFT TO WEAKEN ANY CAP. THIS WEEKEND'S STORMS WILL BE LESS OF A
"RING OF FIRE" PROGRESSIVE MCS SETUP, AND MORE OF A POP UP, HIT OR
MISS, ESPECIALLY INLAND AWAY FROM LAKE MICHIGAN DURING THE
AFTERNOON SATURDAY.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 155 AM EDT SAT JUL 4 2026
RAIN WITH EMBEDDED THUNDERSTORMS ARE MOVING THROUGH SOUTHWEST
LOWER MICHIGAN AT 06Z. AREAS OF MVFR CONDITIONS ARE OCCURRING IN
THE RAIN IN SPOTS, MAINLY DUE TO VISIBILITY. WE EXPECT THE RAIN TO
CONTINUE TO MOVE OFF TO THE EAST IN THE NEXT 2 TO 4 HOURS. THROUGH
09Z-10Z HOWEVER MOST SITES WILL SEE OCCASIONAL MVFR CONDITIONS
WITH SOME ISOLATED THUNDERSTORMS POSSIBLE. THE THUNDER THREAT IS
RAPIDLY COMING TO AN END HOWEVER AS THIS EVENT TRANSITIONS INTO A
STRATIFORM RAIN.
AFTER THE RAIN WE EXPECT SOME MVFR CEILINGS TO FILL IN ACROSS
SOUTHWEST LOWER MICHIGAN, ESPECIALLY TOWARDS THE I-96 TAF SITES.
BY MIDDAY, THE LOW CLOUDS SHOULD HAVE LIFTED AND WE WILL WAIT FOR
A NEW ROUND OF SHOWERS AND STORMS TO DEVELOP SATURDAY AFTERNOON.
THE STORMS WILL DEVELOP IN THE HEAT OF THE DAY IN THE AFTERNOON
AND EVENING FOCUSED WHERE CLEARING CAN DESTABILIZE THE ATMOSPHERE.
BEST CHANCES WILL BE BETWEEN 20Z AND 03Z.
WINDS TODAY WILL VEER FROM SOUTHWEST AT 5 TO 15 KNOTS TO THE WEST.
MARINE
ISSUED AT 239 PM EDT FRI JUL 3 2026
SEVERE THUNDERSTORMS CROSSING SOUTHERN LAKE MICHIGAN THIS
AFTERNOON WITH GUSTS 50 KNOTS. ADDITIONAL SCATTERED STORMS ARE
POSSIBLE LATE THIS EVENING OR OVERNIGHT. WAVES AND SWIM RISK
EXPECTED TO BE FAIRLY LOW THIS WEEKEND IN THE ABSENCE OF STORMS.
A COUPLE SCATTERED STORMS COULD DEVELOP OVER THE LAKE THIS
WEEKEND.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...CAS
AVIATION...DUKE
MARINE...CAS
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