textproduct: Grand Rapids

KEY MESSAGES

- Thunderstorms Possible in SE Lower Michigan This Afternoon

- Frost/Freeze the Next Three Nights

- Rain Likely, Chance Thunderstorm Tuesday

DISCUSSION

Issued at 121 PM EDT Sat May 9 2026

- Thunderstorms Possible in SE Lower Michigan This Afternoon

About 500-750 J/kg of MLCAPE will be present around Jackson this afternoon with little inhibition and moderately steep lapse rates to 700 mb. Some showers or thunderstorms may pop up but chances are iffy as the lower atmosphere will generally have speed divergence. Any storms that do develop could produce hail or gusty winds while quickly moving east and intensifying as they leave our area.

- Frost/Freeze the Next Three Nights

Another cool airmass delivered by the persistent synoptic troughing over the Canadian Shield will bring nightly frost/freeze potential as high pressure noses into the region through Monday night. Mostly clear skies and light winds are favored to set up radiational cooling with object "skin" temperatures reaching near the freezing point while 2-meter temperatures dip into the mid 30s. 2-meter temperatures may outright go below 32 in the typically cooler spots of Central Michigan each night. After a warm and wet March and April, the sensitivity to freezing temperatures is higher than usual.

Can't rule out another frost setup in interior Central Michigan Wed night to Thu morning under the 10-25 percent chance cooler scenarios of a high pressure system quickly moving in behind Tue- Wed's low pressure system. But after that, the pattern does seem to shift toward warmer than normal in the 8-14 day outlook.

- Rain Likely, Chance Thunderstorm Tuesday

An Alberta Clipper type of low will deepen as it moves toward Michigan on Tuesday. Rain is likely in the midlevel warm air and moisture advection ahead of the low. Instability is rather meager in the models as 700-500 mb temperatures will be fairly warm resulting in modest lapse rates, so thunderstorm chances will be less than the likelihood of rain.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 109 PM EDT Sat May 9 2026

Isolated thunderstorms have begun to develop east of the terminals and will continue east through the afternoon. Cannot rule out an isolated thunderstorm at JXN through 21z however confidence is low in terminal impacts. Gusty winds to 30 knots will continue through this evening before diminishing overnight. In addition, skies are forecast to clear out overnight. Winds will remain light into Sunday with scattered Cu development possible beginning late Sunday morning.

MARINE

Issued at 121 PM EDT Sat May 9 2026

Winds are relaxing this afternoon and allowing 3 to 5 foot waves to diminish to 2 to 4. High resolution models suggest a brief surge of northerly winds near Big and Little Sable Points between 8 and 11 PM this evening, with wind speeds about 15-20 knots.

Waves will remain fairly low Sunday and Monday, then strengthening south winds related to an approaching low pressure system on Tuesday will build up hazardous waves for small craft. Hazardous conditions should continue into Wednesday with west- northwest winds.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory from 2 AM to 8 AM EDT Sunday for MIZ037-043>046. Freeze Warning from 2 AM to 8 AM EDT Sunday for MIZ038>040. MARINE...Small Craft Advisory until 3 PM EDT this afternoon for LMZ846>849.