490
FXUS63 KGRR 131742
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
142 PM EDT Sun Jul 13 2025

.KEY MESSAGES...

- Chance for Rain Wed/Thu

&&

.DISCUSSION...
Issued at 132 AM EDT Sun Jul 13 2025

- Chance for Rain Wed/Thu

Zonal flow with weak sfc ridging brings fair weather through
Tuesday then rain chances return for mid-week with the approach
of a weak shortwave trough. Showers and storms arrive Tuesday
night into Wednesday and persist into Thursday as a cold front
moves through. Severe weather threat also increases as forecast
deep layer shear is progged to be 25 to 30 knots along with
sufficient instability for organized storms on Wednesday
afternoon and perhaps into Thursday.

The end of the week features low confidence forecast for details
on where the front stalls and if sfc high pressure builds in.
Showers and a few storms could persist across the southern zones
from Thursday into Friday. Later in the weekend and early next
week is also uncertain as there are indications of an active area
of MCS generation on the northern periphery of an upper high
across the SE CONUS. Some of this convection could make it into
Lower Michigan.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 137 PM EDT Sun Jul 13 2025

Diurnal cu will dissipate as sunset nears leaving broken high
clouds overnight and Monday. Wind will remain light from the west.

&&

.MARINE...
Issued at 137 PM EDT Sun Jul 13 2025

A weak pressure gradient will continue through Tuesday, after
which increasing southwest flow will begin to push waves higher
from north to south. Swim risk at the lakeshore will remain low
through Tuesday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT Monday night for MIZ037>040-
     043>046-050>052-056>059-064>067-071>074.
MARINE...None.

&&

$$

DISCUSSION...Ostuno
AVIATION...04
MARINE...04