247 FXUS63 KGRR 250631 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 231 AM EDT Sat Jul 25 2026 .KEY MESSAGES... - Northwest flow regime continues with occasional chances for rain with low confidence convection forecast && .DISCUSSION... Issued at 230 AM EDT Sat Jul 25 2026 - Northwest flow regime continues with occasional chances for rain with low confidence convection forecast The Great Lakes region remains in between an upper high across the western CONUS and longwave troughing across the eastern CONUS with occasional shortwave troughs passing through and bringing the chance for some much-needed rain. A weakening shortwave trough moves through tonight. Not much moisture available and the best lift is off to the east, so low/slight chance POPs and limited QPF in the current forecast looks good. There is inherent low confidence in the details of how things play out Sunday night through Tuesday given the lack of strong dynamic lifting mechanism, but instability and shear are sufficient for a slow-moving front and weak midlevel vorticity max to focus convection across Minnesota/Wisconsin Sunday afternoon which eventually moves southeast into western Lower Michigan. The failure of the last two similar synoptic scenarios to produce so much as a lightning strike in our forecast area leads to skepticism, but every drought has to end sometime. The front moves through Tuesday with fair weather for mid to late week before the longwave upper trough amplifies with a cold front bringing another chance of rain by next weekend. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 230 AM EDT Sat Jul 25 2026 VFR conditions will continue through Saturday evening. Light winds tonight will increase to 10 to 15 knots from the southwest this afternoon. && .MARINE... Issued at 230 AM EDT Sat Jul 25 2026 Decided to hold off on a SCA/BHS for Saturday afternoon/evening given tendency for observed winds and waves to be lower than model forecasts during southwest flow warm advection set up. The day shift will have to monitor trends, especially around Little and Big Sable points. Gusty winds in thunderstorms are possible Sunday evening into Monday and a SCA/BHS is likely for late Monday and Tuesday as high pressure builds in. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...Ostuno MARINE...Ostuno

NWS GRR Office Area Forecast Discussion