textproduct: Grand Rapids

KEY MESSAGES

- Severe Thunderstorm Risk This Afternoon

- Rain and Thunderstorm Chances Return Friday into the Weekend

DISCUSSION

Issued at 131 PM EDT Mon Jul 27 2026

- Severe Thunderstorm Risk This Afternoon

A Severe Thunderstorm Watch is in effect until 8PM this Evening. The areas of interest are the storms that will move in from Wisconsin and over Lake Michigan into the area. Additional development ahead of the line is possible with remnant boundaries in the current unstable high shear environment. The highest threat for severe thunderstorms will be along and west of US-131 with lower confidence further east as instability decreases.

All hazards will be in play with effective shear values around 50 knots, ML CAPE values increasing to 3000 J/kg, and 0-3km SRH values around 100 to 200 m2/s2. Overall guidance hasn't had a great grasp on thunderstorm development and evolution. We are in a high risk low confidence situation. If storms are widespread through this afternoon and clear this evening, the rest of the night should be largely dry. If the environment isn't worked over we could see additional development overnight.

- Rain and Thunderstorm Chances Return Friday into the Weekend

As the shortwave responsible for today's thunderstorms moves east, pressure heights increase with dry conditions expected through most of the week. Temperatures will largely be in the 80s each day with lows in the 50s and 60s. Rain and thunderstorm chances increase Friday into Saturday with another trough. Chances may linger into Sunday depending on how fast the trough clears the area.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 145 PM EDT Mon Jul 27 2026

A frontal boundary over the northern Great Lakes will move slowing south during the next 12 hours. This will result in continued shower and thunderstorm chances, as front interacts with extremely warm/humid airmass. Expect the storms currently over Lake Michigan to impact MKG/GRR/AZO (in particular) next 1-2 hours. It is unclear how far east the stronger storms will persist. Gusty winds and hail are the greatest threats. Some renewed storm development can't be ruled out behind the current convection into the early evening, and will keep risk of convection through 02-03Z.

Moist airmass and light winds along and immediately behind aforementioned front will result in MVFR ceilings/vsbys in low clouds and fog through much of the night. Winds will eventually become N/NW tonight and Tuesday, and expect the low (MVFR) ceilings to gradually give way to VFR conditions by late Tuesday morning.

MARINE

Issued at 131 PM EDT Mon Jul 27 2026

Severe thunderstorms this afternoon will bring a risk for damaging winds, hail, and waterspouts. This risk is expected until 8pm with it ending earlier to the north. Wave heights of 2 to 3 feet are expected into this evening, but higher waves will be possible with any thunderstorm.

Tonight northerly winds behind the low pick up to 25 to 30 knots and will bring building waves of 4 to 7 feet. These conditions will linger through Tuesday. A Small Craft Advisory and Beach Hazard Statement are in effect. Northwest winds Wednesday afternoon may bring another period of Small Craft Advisory, Moderate to High Swim Risk conditions for areas between Whitehall and South Haven.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Beach Hazards Statement from late tonight through late Tuesday night for MIZ037-043-050-056-064-071. MARINE...Small Craft Advisory from 4 AM Tuesday to 2 AM EDT Wednesday for LMZ844>849.