658 FXUS63 KGRR 191050 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 650 AM EDT Tue May 19 2026 .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 /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 650 AM EDT Tue May 19 2026 Showers and a few thunderstorms moved into Western Lower Michigan within the last hour or so. The activity is running into fairly stable air and has largely dissipated. VCSH is what we are looking at the next 4 to 6 hours given the widely scattered activity. It is not until this afternoon in the 19z to 23z time frame where showers and storms refire in earnest. AZO, BTL, LAN and JXN stand the best chances at thunderstorms this afternoon and evening. There is a chance of MVFR ceilings today, but conditions remain VFR at this point across Lower Michigan. A cold front will sweep through this evening ending any chance for showers or lower ceilings. Wind will be noticeable today from the southwest at 15 to 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. && $$ DISCUSSION...Duke AVIATION...Duke MARINE...Duke

NWS GRR Office Area Forecast Discussion