542 FXUS63 KGRR 200552 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 152 AM EDT Mon Apr 20 2026 .KEY MESSAGES... - Freeze Warning Tonight - Some Storminess by Friday && .DISCUSSION... Issued at 245 PM EDT Sun Apr 19 2026 - Freeze Warning Tonight Sharp upper trough moving through today combined with sufficient low to mid level moisture has resulted in convective updrafts with scattered showers this afternoon. Lake shadow and high clouds has prevented widespread deeper updrafts, lowering the potential for ice pellet/graupel. Showers will diminish end this evening as the trough axis moves east and with the loss of insolation. Cold surface high builds in overnight with drying and subsidence with winds decoupling after midnight. Radiational cooling conditions become optimal by 12Z with the surface high progged to be centered over southwest Lower Michigan. A hard freeze is expected as temperatures will be below freezing for several hours. - Some Storminess by Friday The surface high moves east by Tuesday with southerly flow developing but the moisture return does not immediately result in precipitation as shortwave ridging is expected during the middle part of the week ahead of an upper low over the NW CONUS that eventually moves into Upper Plains and Canada by the end of the week. A cold front trailing a surface low moving into northern Minnesota before it occludes and moves into Canada will concentrate showers on Friday with the chance for thunderstorms during the afternoon. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 152 AM EDT Mon Apr 20 2026 VFR is expected today with light winds underneath a high pressure system. Daytime cumulus development around 5,000 feet is unlikely given the dry lower to middle troposphere. Clouds above 12,000 feet will increase late in the evening. About 25 knots of wind shear between 2,000 feet and ground is possible by 06 Z Tuesday. && .MARINE... Issued at 245 PM EDT Sun Apr 19 2026 High pressure brings tranquil conditions on Lake Michigan tonight and Monday. The high will move east and southerly winds increase and waves will build Monday night. A SCA will be needed from late Monday through Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Freeze Warning until 11 AM EDT this morning for MIZ050>052- 056>059-064>067-071>074. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...CAS MARINE...Ostuno

NWS GRR Office Area Forecast Discussion


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