726
FXUS63 KGRR 261747
AFDGRR

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

.KEY MESSAGES...

- Rain and Thunderstorms Today through Friday

- Hot and Humid Conditions Continue

&&

.DISCUSSION...
Issued at 339 AM EDT Thu Jun 26 2025

- Rain and Thunderstorms Today through Friday

Warm air advection, MUCAPE values of 500-1000J/kg, and a pocket of
higher 850mb moisture is sparking off scattered showers and
thunderstorms this morning along with the low level jet and the
remnant boundary from the storms from Wisconsin.

With the moisture and instability in place throughout the day as
the warm front shifts north scattered showers and thunderstorms
are expected. This afternoon the better chances will be focused
east of US-131 with the potential for some strong to severe
storms. Winds will be the primary concern but can`t rule out the
potential for some small hail.

A lull is possible tonight but we`ll have to monitor the
convection moving out of Wisconsin with the shortwave trough.
Thunderstorms are expected to develop along the front as it moves
through Friday, areas south and east of Grand Rapids have the best
chance with instability building throughout the day. HREF mean
SBCAPE values are around 2000 J/kg with around 25 knots of shear.
While the shear isn`t great, there still is the potential for
stronger storms, especially the farther east you go. Again winds
are the primary concern with any stronger storm.

Within this moist environment, heavy rainfall is likely with any
shower or thunderstorm (rates around 1 inch per hour).
Thunderstorms that track repeatedly over the same area could
cause minor flooding especially in urban areas and known trouble
spots.

Dry conditions return Friday night and continue through most of
the weekend. The arrival of a longwave trough and a parade of
embedded shortwaves will bring the potential for showers and storms
back later Sunday into the work week next week.

- Hot and Humid Conditions Continue

Dew points will continue to be in the 60s and 70s through the
weekend and even into next week. With highs mainly in the 80s,
heat indices will be in the 90s more days than not through the
weekend (Saturday looks to remain in the 80s). At this time not
expecting values to reach 100 or more, but still take care by
staying hydrated and limiting time outside.

&&

.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...RAH/Thomas
AVIATION...04
MARINE...04