012 FXUS63 KGRR 212323 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 723 PM EDT Tue Jul 21 2026 .KEY MESSAGES... - Cooler Midweek Then Warming Up Into The Weekend - Chance of Thunderstorms Sunday-Monday && .DISCUSSION... Issued at 309 PM EDT Tue Jul 21 2026 - Cooler Midweek Then Warming Up Into The Weekend Scattered showers and isolated thunderstorm cells will persist into the evening amid breezy northwest winds and cold air advection. On Wednesday, 850 mb temperatures around 8 C will keep highs no warmer than the mid 70s even under mostly sunny skies, our coolest day since June 26. The large-scale wave pattern remains rather steady-state for the rest of the month, with an upper-level high over Colorado and the Southwest, and troughing over the eastern Great Lakes. Shortwaves will occasionally traverse this flow regime. Heat is expected to build out west and then wash over Michigan this weekend. Ensembles are nearly unanimous on the warming trend Thursday into Sunday, then diverge from Monday onward. Temperatures are favored to climb to around 90 on Sunday with the higher and more uncomfortable dew points also arriving on that day. - Chance of Thunderstorms Sunday-Monday Along with the arrival of warmer and more humid air on Sunday, steeper midlevel lapse rates advecting over the region will also serve to increase instability. Another fairly robust shortwave trough and associated surface low moving across the northern Great Lakes will provide the next chance of thunderstorms between Sunday and Monday. Meaningful differences do exist on the exact track and arrival time of the low, and that means confidence in the threat heavy rain or severe weather is relatively low for our area at this time. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 723 PM EDT Tue Jul 21 2026 VFR conditions expected to continue through Wednesday afternoon. Northwest winds will gust over 20 knots this evening then decrease to about 10 knots overnight. && .MARINE... Issued at 309 PM EDT Tue Jul 21 2026 Moderate to high swim risk is ongoing with 2-4 or 3-5 ft waves at West Michigan beaches. Waves are expected to increase later this afternoon through evening as 20-30 knot winds from the north are channeled down the length of Lake Michigan. There could be some gale force gusts to 35 knots near the Sable Points this evening. Waves peak tonight at 5-10 feet then slowly subside on Wednesday, but will remain hazardous to small craft and swimmers all day. Upwelling of colder water along portions of the West Michigan the shoreline is likely. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement through Wednesday evening for MIZ037-043- 050-056-064-071. MARINE...Small Craft Advisory until 11 PM EDT Wednesday for LMZ844>847. Gale Warning until midnight EDT tonight for LMZ848-849. Small Craft Advisory from midnight tonight to 11 PM EDT Wednesday for LMZ848-849. && $$ DISCUSSION...CAS AVIATION...Ostuno MARINE...CAS

NWS GRR Office Area Forecast Discussion