393
FXUS63 KGRR 301910
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
310 PM EDT Wed Jul 30 2025

.KEY MESSAGES...


- Showers and Storms possible tonight into tomorrow morning

- Smoke and Haze into Friday

- Cooler and less humid through the weekend

&&

.DISCUSSION...
Issued at 305 PM EDT Wed Jul 30 2025

- Showers and Storms possible tonight into tomorrow morning

A short wave trough coupled with a cold front will move through the
area tonight into tomorrow. Currently lower Michigan is underneath a
fairly stable air mass. Convection this morning that crossed Lake
Michigan subsequently weakened and dissipated. While there was a
weak low level jet, there wasn`t any CAPE to sustain storm growth.
The question this afternoon and evening is how far north will the
boundary move. The boundary treks eastward late this afternoon
and evening. While that will bring some instability, temperatures
remain in the low to mid 80s and given the showers out ahead,
will decrease convective development. The best CAPE remains
through IN though latest CAMS does bring some scattered storms
potentially along the I 94 corridor between 22Z to 04Z.

The bigger concern this evening and overnight will be locally heavy
downpours. Weak surface flow along with 1.5 inch PWATS will allow
for a decent environment that any storm will be an efficient rain
producer. The boundary is expected to sprawl and potentially
stall along the I 94 corridor. The Probabilistic precipitation
portal, along with NBM and WPC guidance has 1 to 2 inches of QPF
south of the I 94 corridor through 18Z Thursday. There remains
some questions where the heaviest rain will be. However, given the
potential, WPC has a slight risk for excessive rainfall along and
south of I 94. If any training of showers/storms occurs there
could the potential for minor flooding.

   While rainfall will overspread the region, this is not expected
to be a drought buster for much of the region. The I 94 corridor
will receive the heaviest rain and any drought conditions there
should be helped. However, between the I 96 and I 94 corridors is
only expected to receive around a half an inch.

- Smoke and Haze into Friday

  You may have noticed some hazy/smoky conditions, especially along
the US 10 corridor earlier this week. While the precipitation has
subdued it, the smoke/haze from Canadian wildfires is expected to
linger across the region through Thursday. This is why EGLE has
issued an air quality advisory.

- Cooler and less humid through the weekend

    As the frontal boundary moves to the east, cooler and drier air
will filter in behind the front which will bring an end to this
weeks heat. Temperatures will drop back into the upper 70s into the
weekend, peaking into the mid 80s by Monday.

    High pressure will continue to build over the Midwest and
dominate the weather pattern over the Great Lakes through the
weekend and into next week. Next precipitation chance should be
late Monday into Tuesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 134 PM EDT Wed Jul 30 2025

Rain showers over the lake will arrive in West Michigan over the
next several hours. Conditions will be mainly VFR through the
evening, though isolated thunderstorms bringing MVFR and lower
conditions are possible. Tonight, more widespread rain will
concentrate near the I94 corridor with MVFR conditions expected.
Cigs could reach IFR levels for AZO/BTL/JXN however confidence is
to low for TAF inclusion at present. High pressure moving in
Thursday morning will cause conditions to improve to VFR levels.

&&

.MARINE...
Issued at 310 PM EDT Wed Jul 30 2025

Fairly light winds along the lakeshore remain predominately from
the northeast. Light showers will overspread the lake as the
afternoon continues. With the weak front moving into the region
there remains the chance that as the winds shift to the
north/northwest they increase to 15 to 20kts. However, given the
stable environment and overall weak flow, expected the waves to
peak into the 2 to 4ft range. So while this does creep into the
moderate beach hazard range, the flow will be mostly offshore, and
any threat will be short lived. For those reasons, have not issued
any headlines. Highest waves remain possible along the points and
south of Saugatuck after 7 PM.
 The strong north flow today and tomorrow should pull the warmer
waters offshore, causing upwelling. That could lower nearshore
lake temperatures by tomorrow afternoon and into the weekend. Lake
temps should drop into the upper 40s to low 50s.


&&

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

&&

$$

DISCUSSION...Ceru
AVIATION...Thomas
MARINE...Ceru