829 FXUS63 KGRR 052350 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 750 PM EDT Sat Sep 5 2026 .KEY MESSAGES... - Fair Weather through Labor Day - Chance for showers and Thunderstorms Tuesday and Wednesday && .DISCUSSION... Issued at 157 PM EDT Sat Sep 5 2026 - Fair Weather through Labor Day An Omega block develops across the CONUS this weekend as the central U.S. upper high is bookended by cut off lows across the NE and NW CONUS. This lowers heights across the central Great Lakes and allows surface high pressure ridge to build in from the northeast with lower temperatures and dew points. Showers end this afternoon and clearing pushed south this evening with it becoming noticeably cooler overnight. Morning lows on Sunday and Monday expected to be in the upper 40s to lower 50s across the northern forecast area. - Chance for showers and Thunderstorms Tuesday and Wednesday The surface high retreats east eastward by Tuesday. The Omega block breaks down as a low across the Pacific NW kicks east and flattens the upper high, with surface low pressure tracking across southern Canada. Return flow of moisture and a surface warm front should kick off some showers and thunderstorms late Tuesday into Wednesday. Another round of storms will be possible as a cold front moves through late Wednesday and shear profiles suggest strong storms are possible if instability is sufficient. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 750 PM EDT Sat Sep 5 2026 Skies are trending mostly clear tonight following a fairly cloudy day with some rain showers in southwest Michigan. Dew points at the surface are still fairly high compared to the expected low temperatures tonight. Some of the high resolution models are developing fog or LIFR ceilings for pre-sunrise Sunday. The one thing that might keep fog in check is 15-20 knot winds at 500 feet. Seems reasonable to plan on the potential for IFR ceilings or visibility between 07 and 13 Z, though it is medium confidence. && .MARINE... Issued at 157 PM EDT Sat Sep 5 2026 Light offshore winds, generally less than 15 knots, can be expected through Monday. High pressure will move east on Tuesday and winds will be on the increase, with a Small Craft Advisory probably being needed for Tuesday and Wednesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...CAS MARINE...Ostuno

NWS GRR Office Area Forecast Discussion