textproduct: Grand Rapids

KEY MESSAGES

- Frost Expected Along and North of M-20

- Periods of Rain Friday through the Weekend

- Warming Up Next Week With Slight Chances (20 percent) for Rain

DISCUSSION

Issued at 143 PM EDT Wed May 20 2026

- Frost Expected Along and North of M-20

Colder temperatures move in tonight with 925 mb temperatures around 4 to 5 C and a weak inversion in place. Lows tonight drop into the low 30s to low 40s from north to south. The best potential for frost will be along and north of M-20 where there is a higher probability (60 to 90 percent) of temperatures falling below 37 F. Therefore this area has been included in the Frost Advisory.

Further south temperatures are expected to be largely above 37 F, but some isolated low lying areas could briefly fall below before sunrise. Winds further south are less likely to be calm and therefore will help keep temperatures warmer. Any increase in cloud cover would also keep temperatures from falling lower.

- Periods of Rain Friday through the Weekend

High pressure sticks around for one more day Thursday. Some showers may try to move in from the west Thursday afternoon, but dry air should keep anything from reaching the ground.

Upper level divergence will be present Friday into Saturday with a shortwave moving through. There are some differences with the timing and location of the low as it moves through. Overall the best chances looking at the cluster analysis will be Friday night into Saturday. There will be some instability which could result in some embedded thunderstorms overnight into Saturday. The best chance for any thunder will be south of I-96. Another shortwave moves through Sunday bringing more chances for rain and thunderstorms. The best chances (40 to 50 percent) are along and east of a Kalamazoo to Alma line.

- Warming Up Next Week With Slight Chances (20 percent) for Rain

Upper level ridging builds in for next week with warming temperatures and some slight chances (20 percent) for rain and thunderstorms. These showers and storms could be more of the afternoon pop up variety as there isn't any great source of lift for anything more widespread. Temperatures will warm each day with highs in the upper 70s to mid 80s and lows in the 50s.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 143 PM EDT Wed May 20 2026

VFR prevails this afternoon now that stratocumulus clouds have gone scattered/broken above 3,500 feet. The lower atmospheric clouds will continue to dissipate going into this evening, though some models such as the HRRR want to hang on to moisture and clouds around 3,000 feet for a period between 02-08 Z tonight, moving from JXN toward AZO.

MARINE

Issued at 143 PM EDT Wed May 20 2026

Northerly winds and waves continue to build this afternoon with High Swim Risk Conditions and Small Craft Advisory conditions expected from Grand Haven and to the south. Winds and wave heights will decrease tonight with winds becoming more easterly into Thursday. Winds further offshore will remain from the north before shifting to the northeast Thursday night. Friday winds build once more to Small Craft Advisory levels as a low pressure system tracks toward the area. Rain and a few thunderstorms will be possible Friday night into Saturday with the best chances for lightning south of Grand Haven.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory from 1 AM to 9 AM EDT Thursday for MIZ037>040- 043>046. Beach Hazards Statement through late tonight for MIZ056-064-071. MARINE...Small Craft Advisory until 2 AM EDT Thursday for LMZ844>846.