textproduct: Grand Rapids

KEY MESSAGES

- Showers and storms today, some may be strong southeast of GRR

- Cooler and drier air settles in for Wednesday and Thursday

- Unsettled weather for Friday into the weekend

DISCUSSION

Issued at 358 AM EDT Tue May 19 2026

- Showers and storms today, some may be strong southeast of GRR

A decaying area of showers and embedded thunderstorms are slowly pushing east from Wisconsin and Illinois at 345am with some scattered development over Lake Michigan. We expect the main area to move into the lakeshore counties between 600am and 800am. This activity should remain on the weak side given limited instability. It is being aided however by strong low level moisture transport which can never be underestimated. We will be monitoring but this convective activity should remain below severe criteria.

The focus will then become the redevelopment this afternoon and early evening along and ahead of the advancing cold front. We are relying on the HREF for timing and location. We expected showers and storms to reintensify southeast of a line from Holland to Grand Rapids to Lansing. Storms should move through our southeast CWA (AZO, BTL, LAN and JXN) between 400pm and 800pm. MUCAPE values are more than adequate, forecast to be between 1,000 and 2,000 j/kg. The best shear lags the front, so deep layer values will only be in the 20-30 knot range. Bottom line severe weather is possible with wind being the main threat especially towards JXN. 35 knot winds at 850mb and 50 knots at 500mb support that thinking.

- Cooler and drier air settles in for Wednesday and Thursday

850mb temperatures plunge as we head into Wednesday behind the cold front. +2C to +3C air will be over a large portion of the CWA on Wednesday which will hold highs to the 50s over Central Lower and the 60s to the south. Lows Wednesday night will reach the 30s over Central Lower and we will likely need Frost/Freeze headlines. The cool and dry weather will continue into Thursday as surface high pressure slides through the Great Lakes. Highs on Thursday will be in the low to mid 60s area wide.

- Unsettled weather for Friday into the weekend

The models continue to show rain spreading back into the Great Lakes from the south and southwest on Friday. The rain chances will linger into the weekend. Embedded shortwaves in a developing southwest flow will be the culprit for the precipitation as will be weak front and surface low. Highs will warm into the 70s over the weekend. The south could see 0.50 to 0.75 inches of rain from Friday into Saturday.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 233 AM EDT Tue May 19 2026

Showers and storms are located upstream over Wisconsin and Illinois making slow progress to the east. We expect these decaying showers/storms to move into Western Lower Michigan between 10z and 12z. The decaying activity will move through the TAF sites during the morning. MVFR ceilings will also develop for places like MKG, GRR and AZO associated with the moisture increase. There will be a lull in the midday hours with a redevelopment of stronger storms for AZO, BTL, LAN and JXN between 20z and 02z. These storms will be capable of poor aviation conditions (IFR and lower) along with strong winds in excess of 40 knots. The showers and storms should taper off after 02z as a cold front presses south through the area. VFR weather is expected into the overnight.

In general, winds will be strong today out of the south and southwest. Speeds will generally be between 15-30 knots.

MARINE

Issued at 358 AM EDT Tue May 19 2026

We have extended the Small Craft Advisory on Lake Michigan through 800am Wednesday for all zones between St. Joseph and Manistee. Strong southwest winds to 30 knots can be expected today before switching to the northwest behind the passage of a cold front this evening. The northwest winds this evening will push towards 30 knots as well which is the reason for extending the SCA in time.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.