textproduct: Grand Rapids

KEY MESSAGES

- Extreme Heat Today Through At Least Thursday

- Chances for Storms Later in the Week

DISCUSSION

Issued at 308 AM EDT Tue Jun 30 2026

- Extreme Heat Continues Through At Least Thursday

No change for the expectations of today being the first of three straight days with very dangerous heat and humidity. Highs in the 90s with lows in the upper 70s will be common Tuesday through Thursday with heat index values during the day into the 100s and in the nighttime period in the mid to upper 80s. Friday is likely to see some relief as the upper ridge weakens...though highs Friday may only be about 5 degrees or less cooler than the rest of the week. A little more relief (though it still will be hot) comes over the holiday weekend when high temperatures in the mid 80s will be common.

- Chances for Storms Later in the Week

Still expecting a series of shortwaves to try and weaken the ridge over us the rest of the week. Some of these waves could bring showers/thunderstorms to southern Lower Michigan. Generally the greater severe risk will remain over the Upper Peninsula and northern lower...but instability is good enough over southern lower to keep a non-zero severe threat. Hard to pick which days or timeframes are best for storms and/or any possible severe weather...though the severe risk does creep a little further south each day through Thursday.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 136 PM EDT Tue Jun 30 2026

Areas of MVFR ceilings affecting some of the terminals are expected to change into a scattered layer above 3000 ft this afternoon. It is interesting to note that multiple cloud layers in the 2000-3000 ft range have been reported at some of the terminals having automated ASOS observations. This suggests that stratocumulus is indeed breaking up because this process can often trick the small diameter, upward pointing cloud sensors as well as the averaging algorithms associated with the ASOS platforms.

Other than that, have tried to capture the gusty nature of winds with gusts expected to subside around or shortly after 00Z.

MARINE

Issued at 200 PM EDT Tue Jun 30 2026

Beach reports, webcams, and buoys indicate a moderate bordering on high swim risk ongoing today, with the wave spectrum generally 2 to 4 feet near and north of Holland. South-southwest winds over the lake at about 15 knots will induce some longshore currents and structural currents particularly affecting south piers.

The Port Sheldon and Ludington buoys significant wave height around 2.5 feet is less than what we have in the forecast, as the NBM winds have been a little high and the winds have been less effective at imparting momentum onto the water in this highly stable marine air layer. Models indicate a slight uptick in winds possible this afternoon, so will hold on to this low-end Small Craft Advisory and Beach Hazards Statement until its planned expiration at 8 PM.

Another 2-4 foot wave and moderate swim risk day is expected on Wednesday. Thunderstorms on Wednesday, if they develop over Wisconsin as indicated by some models, may cross central Lake Michigan and could produce locally strong wind gusts.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ037- 043-050-056. Extreme Heat Warning until 8 PM EDT Thursday for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. Air Quality Alert until midnight EDT tonight for MIZ050-056-057- 064-071. MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ846>849.