146 FXUS63 KGRR 221800 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 200 PM EDT Sat Aug 22 2026 .KEY MESSAGES... - Scattered Showers and Thunderstorms this Afternoon - Cooler with Slight Chances (20 percent) for Showers Sunday - Midweek Rain Chances && .DISCUSSION... Issued at 200 PM EDT Sat Aug 22 2026 - Scattered Showers and Thunderstorms this Afternoon The upper level trough will continue to move through lower Michigan today. The front is currently around a Midland to Battle Creek line and shifting east. Expect isolated to scattered showers and thunderstorms along and ahead of the front before it clears later this afternoon. We`ll still be under the upper level trough until tonight with some positive vorticity advection moving through the flow. Moisture is limited, but can`t rule out an isolated shower this evening. Northwest winds pick up behind the front with gusts around 20 to 30 mph before the inversion builds in this evening. Warmer lake temperatures with dropping 850mb temperatures may keep the air mass unstable enough along the lakeshore for some spotty showers into early Sunday (20 percent chance). - Cooler with Slight Chances (20 percent) for Showers Sunday The upper level low will remain over the eastern Great Lakes continuing some slight chances (20 percent) in the northwest flow. Another surge of positive vorticity advection is expected to move through the afternoon which could add additional support for shower development along with some diurnal shallow instability. The best chances will be north of I-96 and taper off Sunday evening. Northwest winds will continue to be breezy with gusts to 30 mph during the day. Temperatures will be a little cooler than today with highs in the upper 60s to low 70s. - Midweek Rain Chances A shortwave ridge moves in for the beginning of next week but it will be short lived. Heights begin to fall with the approaching trough Wednesday into Thursday. Warm air advection may spark off showers and thunderstorms late Tuesday night into Wednesday morning, otherwise the best chances (50 to 70 percent) hold off until Wednesday night when the trough axis is expected to move through. A lull is possible Thursday morning before chances increase (30 to 50 percent) again with the daytime heating Thursday afternoon. Monday will be the coolest day of next week with highs in the 70s. Temperatures then warm into the low 80s for the rest of the week. Low temperatures will largely be in the 50s with some spots dropping into the 40s Monday and Tuesday morning. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 200 PM EDT Sat Aug 22 2026 Cold front extends from vicinity of Saginaw Bay southwest to near JXN early this afternoon. Scattered convection continues to percolate along front, and LAN/JXN will run a risk (30-40%) for a shower or storm through roughly 19-20Z. MVFR ceilings/vsbys will remain possible at LAN/JXN through 19-20Z as well. Thereafter, VFR conditions are expected across West Michigan through the remainder of the TAF period. Skies will be mostly clear tonight, with perhaps some patchy 3-4kft Strato-CU in northwest flow cold air advection pattern. With 850 mb temps falling to 7-8C and water temperatures of +21-22C, influence of Lake Michigan will need to be monitored overnight, especially at MKG. This may yield slightly gustier winds and perhaps an increase in lower clouds. Expect an uptick in CU after 14-15Z Sunday, given cooler air aloft. NW winds will prevail behind cold front through 18Z Sunday, with occasional gustiness around 20 kt this afternoon and again beginning late morning Sunday. && .MARINE... Issued at 200 PM EDT Sat Aug 22 2026 High Swim Risk and Small Craft Advisory conditions continue through Sunday. Northwest winds with gusts to 30 knots will cause waves to continue to build into Sunday with wave heights peaking around 5 to 7 feet Sunday afternoon. Waterspouts will also be possible tonight into early Sunday morning with the best chances toward southern Lake Michigan. Winds and waves slowly come down Sunday night into Monday. Another period of Small Craft Advisory and High Swim Risk conditions is possible Wednesday along with our next chance for showers and thunderstorms. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement through Sunday evening for MIZ037-043- 050-056-064-071. MARINE...Small Craft Advisory until 11 PM EDT Sunday for LMZ844>849. && $$ DISCUSSION...RAH AVIATION...Smith MARINE...RAH

NWS GRR Office Area Forecast Discussion