021
FXUS63 KGRR 300706
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
306 AM EDT Sun Aug 30 2026

.KEY MESSAGES...

- Scattered Showers, Isolated Thunderstorms Today

- Hot and Humid with Additional Chances for Thunderstorms

&&

.DISCUSSION...
Issued at 305 AM EDT Sun Aug 30 2026

- Scattered Showers, Isolated Thunderstorms Today

Scattered showers are developing within an area of 850-700mb warm
air advection along with low level convergence from the 850mb low
level jet. Instability is limited (100 to 500 J/kg) largely over
Lake Michigan and then along and south of a Ludington to Jackson
line. An isolated thunderstorm is possible with the best chances
toward Lake Michigan as seen in recent lightning observations.

The best convergence and warm air advection will gradually shift
east through this morning and early afternoon before most of the
area clears out around 2pm. Some lingering showers and storms are
possible toward central lower Michigan through the afternoon and
early evening.

- Hot and Humid with Additional Chances for Thunderstorms

High temperatures this week will be in the 80s to low 90s with the
hottest temperatures on Tuesday and Wednesday. Dew points this
week will also be in the 60s to around 70. This will result in
heat index values in the upper 80s to 90s. Some spots toward
southern Michigan may see heat index values hit 100. Temperatures
cool down for the rest of the week as northerly flow returns.

Within our hot, moist environment any little disturbance could
spark off showers and thunderstorms through the first half of the
week. The low level jet and warm air advection will play a role
tonight into Monday morning and Monday night into Tuesday. A warm
front will lift through the region Tuesday night into Wednesday
morning with a cold front moving through Wednesday evening. There
is some uncertainty with how far south showers will extend until
Wednesday. Overall wouldn`t be surprised if PoPs needed to be
trended higher for tonight into Monday morning and on Tuesday.
More ensemble members than not have precipitation, with the best
chances Monday morning, Tuesday morning, and Tuesday night into
Wednesday morning.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 146 AM EDT Sun Aug 30 2026

VFR conditions are expected today with periods of showers at least
through 18Z. Isolated thunder is possible more toward GRR and MKX,
therefor added a PROB30 group at these sites. There is lower
confidence for thunder at the other sites, however if we did see
an isolated thunderstorm it would be between 15-18Z. Reduced
visibilities will be possible if thunderstorms develop.

Low level wind shear is possible early this morning as the low
level jet moves overhead. Southwest winds then pick up this
afternoon with gusts around 20 to 25 knots.

&&

.MARINE...
Issued at 305 AM EDT Sun Aug 30 2026

South to southwest winds will increase this afternoon with gusts
to 25 knots. Waves will build to around 3 to 6 feet with the
highest wave heights north of Holland. A Small Craft Advisory and
Beach Hazard Statement are in effect. Lighter winds are expected
tonight into Monday morning, but winds may pick back up with gusts
20 to 25 knots Monday afternoon resulting in another brief period
of high waves.

Scattered showers and isolated thunderstorms are expected this
morning, with drier conditions moving in for the afternoon.
Chances for showers and thunderstorms return tonight into Monday
morning with additional chances (20 to 40 percent) through the
rest of the week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through this evening for MIZ037-043-050-
     056-064.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849.

&&

$$

DISCUSSION...RAH
AVIATION...RAH
MARINE...RAH