988 FXUS63 KGRR 182310 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 710 PM EDT Thu Sep 18 2025 .KEY MESSAGES... - Showers and a Few Storms This Evening, Fog Returns Tonight - Cooler and Unsettled Weather This Weekend Through Early Next Week && .DISCUSSION... Issued at 325 PM EDT Thu Sep 18 2025 - Showers and a Few Storms This Evening, Fog Returns Tonight We remain under the general influence of high pressure, with ample sunshine across much of Lower Michigan continuing today as temperatures again surge into the mid 80s, which is about 10 degrees warmer than normal for this time of year. However, some change is on the horizon. Showers and a few thunderstorms have formed and persisted throughout much of the day over Northern Lake Michigan. This area is slowly working its way south and east toward Ludington as of this writing. Numerical guidance continues to struggle mightily with this area of convection, although with some low-level convergence and several hundred joules of CAPE it`s not a complete shock to see some slow- moving showers/storms. Models continue to focus primarily on our northeast corner counties (Clare, Osceola, Isabella) with convective development over the next few hours, so the expectation is that the ongoing weather along the lakeshore will continue to morph eastward with time. Despite occasional flashes of lightning, these storms are not severe, and the main impact will be some localized beneficial rain totals around one-half inch or so. Low-level winds become prevailing out of the northeast overnight as surface high pressure shifts into position northeast of Lower Michigan. This will bring moist flow directly off Lake Huron and spread it across much of the area. As evening showers and storms diminish after sunset, and temperatures begin to cool, we`re expecting even more robust fog formation than we`ve seen the last few nights. Fog will be thicker in east and northeast parts of the area due to proximity to Lake Huron, but at least patchy fog is likely across most of the area. This will burn off shortly after sunset on Friday, though, giving way to sunshine and a final day with temperatures in the 80s south of I-96. Clouds and cooler temperatures will likely linger over the more northern areas tomorrow. - Cooler and Unsettled Weather This Weekend Through Early Next Week The upper-level ridge axis passes through Lower Michigan Friday morning, which begins a transition of our weather pattern into more broad southwesterly flow. This will bring in additional moisture and generally unsettled weather to the area starting this weekend and continuing through at least the middle of next week. Temperatures will steadily return to more seasonably cool conditions, with high temperatures in the 70s. Rain/shower chances increase during this period as the remnants of the broad upper low currently in the High Plains pass near/north of Michigan with accompanying shortwave troughs moving through Lower Michigan. While none of batches of showers or storms over the next several days carry much of a risk of heavy rain, the sheer number of rain chances should eventually result in beneficial rain for most places, with WPC 7-Day QPF on the order of 0.50 to 1.0 inches across virtually our entire area. While this won`t reverse the ongoing drought conditions, it should provide at least some relief. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 709 PM EDT Thu Sep 18 2025 Conditions are VFR at present with scattered clouds around 6kft near LAN/GRR associated with the storms that passed north of the terminals. Tonight, easterly flow off of Lake Huron will bring fog and low stratus potential into West Michigan, but some uncertainty exists as to how far conditions fall and how far west restrictions will extend. This is due to scattered cirrus across the area which will somewhat reduce radiational cooling. The worst conditions will be at LAN and JXN which are closest to the moisture source region. MVFR is likely with IFR or lower conditions possible if more substantial clearing develops. GRR is near the likely western extent of the best low-level moisture so conditions are more uncertain, with any MVFR conditions that do develop being more intermittent. AZO, BTL, and MKG currently are left out of any restrictions. However, if radiational cooling overperforms/low- level moisture quality is better than expected MVFR or lower conditions could extend further west into these sites. Any clouds/fog will burn off shortly after sunrise. && .MARINE... Issued at 325 PM EDT Thu Sep 18 2025 Light northwesterly winds today become easterly Friday with waves remaining below Small Craft Advisory levels through this time. Increasing gradient winds of 15-20 knots from the east develop Friday Night with Small Craft Advisory level gusts possible over the waters. Winds subside to the 10-15 knot range for the weekend, with winds from the southeast on Saturday and from the southwest Sunday. A few rounds of showers and thunderstorms are possible Saturday through early next week as a disturbance crosses the Great Lakes region. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...AMD AVIATION...Thomas MARINE...Thomas

NWS GRR Office Area Forecast Discussion