955
FXUS63 KGRR 261818
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
218 PM EDT Thu Jun 26 2025

.KEY MESSAGES...

- Highest Chances for Rain will be Friday and Monday

&&

.DISCUSSION...
Issued at 217 PM EDT Thu Jun 26 2025

Diurnally-enhanced convection along a warm front will persist
into this evening then should diminish overnight. More storms will
fire up on Friday in the warm sector and ahead/along a cold front
as a sfc low tracks across northern Lower Michigan. The front
clears southeast zones late Friday night with a brief period of
fair weather and lower dew points into Sunday morning.

By Sunday afternoon, return flow is already setting up as a
shortwave trough embedded in zonal flow moves from the Plains
into the Great Lakes. Dew points surge back into the 70s by Monday
with a cold front arriving by afternoon. Instability is
sufficient for enhanced thunderstorm coverage but deep layer
shear is only around 20 to 25 knots, so storms may be more of the
pulse variety.

Dew points behind the front fall into the 50s to lower 60s for
Tuesday through Thursday offering a break from the recent
oppressive humidity. Long range indications are for the
possibility of some storminess on the 4th, but confidence is low
in the details.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 139 PM EDT Thu Jun 26 2025

An unstable airmass exists across the region this afternoon. A
frontal boundary stretches across the cwa just north of I-96 where
dewpoints are in the 60s; 70s south of there.

Showers and storms are moving across the southern terminals where
strong winds/microbursts will be possible this afternoon.

More storms are expected to develop over Wisconsin tonight and
then move east as the aforementioned frontal boundary begins to
lift north. This may result in more convective development; we
included a PROB30 mention for that potential.

&&

.MARINE...
Issued at 139 PM EDT Thu Jun 26 2025

Waves will build to around 2 feet north of Holland Friday
afternoon. Otherwise waves will generally be less than 2 feet for
the next couple of days.

Thunderstorms remain a possibility this afternoon and again Friday
afternoon.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Ostuno/RAH/Thomas
AVIATION...04
MARINE...RAH