481 FXUS63 KGRR 072309 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 709 PM EDT Tue Jul 7 2026 .KEY MESSAGES... - Slow moving front brings rain, storms late week - Upper High builds in early next week && .DISCUSSION... Issued at 201 PM EDT Tue Jul 7 2026 - Slow moving front brings rain, storms late week Quasi-zonal flow regime this week with upper height falls attending a slow-moving cold front sagging south through the Great Lakes. We will see chances for showers and thunderstorms from Wednesday night through Friday as the front becomes almost parallel to the flow. By Thursday, training of storms could result in minor flooding but in most areas rainfall should be beneficial rather than excessive. Severe weather chances are marginal Wednesday night with limited instability and deep layer shear. - Upper High builds in early next week The rains should end across the southern zones over the weekend as the front sags south then large scale subsidence and drying begins with an upper high across the Northern Plains edging into Lower Michigan. Expect warm and dry for early next week before heights fall as an upper trough amplifies across eastern Canada. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 708 PM EDT Tue Jul 7 2026 Any remaining Cu will diminish after sunset with limited Cu development possible again on Wednesday around 5kft. Can`t rule out some patchy ground fog overnight, with the best signal at JXN which climatologically is also our favored site for fog development. Have not included restrictions at any terminal besides JXN given low confidence (20-30% chance) of MVFR conditions at these sites, with moderate confidence (near 50%) at JXN. Any fog that develops will diminish shortly after daybreak given strong July mixing with VFR conditions then expected through the end of the TAF period. Winds will become light and variable overnight before increasing to 5-8 knots from the southwest on Wednesday. && .MARINE... Issued at 201 PM EDT Tue Jul 7 2026 Fairly tranquil weather this week except for the possibility of thunderstorms with gusty winds and heavy downpours Wednesday night into Thursday morning. Wind direction will be frequently changing with north winds tonight going south on Wednesday then north again on Thursday and Friday, but generally remaining at or below 15 knots. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert from midnight tonight to midnight EDT Wednesday night for MIZ050-056-057-064-065-071. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...Thomas MARINE...Ostuno

NWS GRR Office Area Forecast Discussion