401
FXUS63 KGRR 232254
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
654 PM EDT Tue Jun 23 2026

.KEY MESSAGES...

- Showers/storms Wednesday, then clearing Thursday

- 70s through Friday, then heat

&&

.DISCUSSION...
Issued at 200 PM EDT Tue Jun 23 2026

- Showers/storms Wednesday, then clearing Thursday

HIgh pressure and sunny skies this afternoon will soon be replaced
by an Alberta Clipper Wednesday; This type of system is usually
more indicative of winter through mid spring, but this has been a
relatively cool stretch of weather and we`ve have one more clipper
to go before the heat develops.

The clipper is currently nearing the Canada/Montana border and
will move across the northern Great Lakes tonight and Lower MI
Wednesday. Clouds will advect over the region late tonight and
showers and storms will move in either late tonight or early
Wednesday. The northwest cwa should see precipitation first.
Despite meager mid level lapse rates...5-5.5C/Km...this system
will also arrive with a push of moisture. A 35kt llj will move
over the cwa Wednesday coincident with a plume of 1.5 inch
precipitable water. More importantly, models show 40-45kts of bulk
shear Wednesday afternoon. These dynamics should be enough to
generate storms and a few could be strong to perhaps severe.

High pressure will build in from the north Thursday and last
through much of the weekend before we under a pattern change.

- 70s through Friday, then heat

A deepening upper trough over the northern Rockies will result in
a building upper ridge over the Great Lakes late in the weekend
and early next week. The increasing heights will result in highs
moving through the 80s to perhaps 90; it`ll feel more like summer.
Dewpoints will also climb into the mid to upper 60s to make it
very humid. Apparent temperatures by Monday and Tuesday are
likely to be in the upper 90s to lower 100s.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 654 PM EDT Tue Jun 23 2026

Scattered diurnal Cu will diminish over the next several hours
with mainly mid and high clouds expected overnight. Expect winds
to be light and variable overnight.

Aviation conditions deteriorate late morning into early afternoon
Wednesday as showers increase thanks to a nearby warm front. The
worst conditions will be where the heaviest shower concentration
is, currently favored for MKG/GRR/LAN with lower confidence in
restrictions for AZO/JXN/BTL. MVFR conditions are favored in
restrictions with a low chance of IFR in heavier showers (10-20%).
Thunder probabilities are also low (10-20%) based on
NBM/HREF/REFS guidance and marginal forecast instability so will
leave thunder out of the forecast. Showers continue and thunder
chances increase after 00z Thursday. Winds will increase from the
south to around 10 knots as the warm front passes by Wednesday
afternoon.

&&

.MARINE...
Issued at 200 PM EDT Tue Jun 23 2026

Wind will become southerly late tonight and Wednesday and this
will result in higher waves over the northern nearshore zones.
It`s possible we may need a small craft advisory Wednesday
afternoon for the northern 2-3 zones. Additionally, thunderstorms
will likely develop Wednesday which will pose a threat to boaters
and beach goers.

&&

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

&&

$$

DISCUSSION...04
AVIATION...Thomas
MARINE...04

NWS GRR Office Area Forecast Discussion