411
FXUS63 KGRR 311948
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
348 PM EDT Thu Jul 31 2025

.KEY MESSAGES...

- A break from heat and humidity through early next week

- Warming trend next week with increasing humidity and
  shower/storm chances

&&

.DISCUSSION...
Issued at 348 PM EDT Thu Jul 31 2025

- A break from heat and humidity through early next week

Broad upper-level troughing anchored over Ontario/Quebec will
provide high pressure over the Great Lakes and a flow of more
seasonably near-average temperatures over the next several days.
Dew points in the 50s over the weekend will feel far more
comfortable than the frequent 70 degree dew points of late.

Unfortunately, wildfire smoke from the forests of central
interior Canada will be trapped under the high over much of the
region, like today. Guidance from the experimental HRRR-Smoke and
RRFS-Smoke, and also advice from Michigan EGLE, suggests the Lower
Peninsula could see somewhat improved near-surface smoke on
Friday, though it may return for Saturday.

- Warming trend next week with increasing humidity and
  shower/storm chances

High pressure slowly shifting east during next week will provide
us with gentle southeasterly then southerly flow, with a return of
gradually warmer and more moist air from the Atlantic region then
the Gulf. The average of the global model ensembles generally
shows a slow upward trend in temperature, dew point/PW, CAPE, and
QPF potential. The earliest reasonable next chance of showers is
Tuesday, though the chance is fairly low at this time. There is
still quite a spread among the ensemble members regarding day-by-
day instability and QPF chances through late next week, with
generally small and weak weather systems present.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 104 PM EDT Thu Jul 31 2025

Wildfire smoke advected in from Canada is bringing widespread
MVFR visbys across West Michigan this afternoon. As mixing
diminishes this evening visbys are expected to improve to VFR.
Ceilings will be VFR or indefinite over the TAF period. Winds will
be predominantly from the northeast at 10 knots or less. Gusts to
17 knots are possible this afternoon, mainly at Lansing and
Jackson.

&&

.MARINE...
Issued at 348 PM EDT Thu Jul 31 2025

Winds are increasing near Big and Little Sable Points this afternoon
as the lake breeze interacts with the prevailing northeasterly flow.
3-6 foot waves/a high swim risk and gusts to 25 knots are expected
north of Whitehall. Have also added a Small Craft Advisory between
South Haven and St Joseph for 3-5 foot waves, with the St. Joseph MI
buoy already giving wave heights near 4 feet this afternoon. Given
the offshore flow direction for the Van Buren County part of the
shoreline, wave heights will remain in the 2-4 foot range near the
shore so will not expand the Beach Hazards Statement at this time.
Areas between South Haven and Whitehall will also see 2-4 foot waves
and a moderate swim risk this evening.

Another burst of wind will lead to 2-4 foot waves south of Muskegon
Friday afternoon, but wind speeds will be a bit low to warrant a
high swim risk/any headlines. High pressure then keeps winds light
through the weekend. The northerly flow will also support a period
of upwelling which will lead to colder water temps.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT Saturday night for
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.
     Beach Hazards Statement until midnight EDT tonight for MIZ037-
     043.
MARINE...Small Craft Advisory until 5 AM EDT Friday for LMZ844.
     Small Craft Advisory until midnight EDT tonight for LMZ848-849.

&&

$$

DISCUSSION...CAS
AVIATION...Thomas
MARINE...Thomas