638 FXUS63 KGRR 260750 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 350 AM EDT Sat Sep 26 2026 .KEY MESSAGES... - Dry through Tuesday - Rain chances increase mid week - Above normal temperatures expected && .DISCUSSION... Issued at 350 AM EDT Sat Sep 26 2026 - Dry through Tuesday Overall the theme of the forecast has not changed much in the past couple of days. The first point remains the same in that we will see dry weather through the weekend and at least into Tuesday. The east coast low will keep ridging in place across the Great Lakes both at the surface and aloft. BUFKIT overviews remain very dry and all ensemble members of the GFS and ECWMF rain dry as well through Tuesday. Bottom line a high confidence forecast that conditions remain benign and dry for the next 4 days. - Rain chances increase mid week The setup changes as we head into mid week. The reason for this is largely a shortwave moving across Canada in zonal flow. The shortwave acts to flatten the ridge over the Great Lakes and pulls the east coast system northward into the westerlies. What this means for the Great Lakes is some active weather as the ridge that was over the region will be gone. Models show good chances for rain beginning as early as Tuesday night, but more likely on Wednesday. At this point details are not certain in the mid to late week time frame but it does look like good opportunities for rain. The first opportunity will come on Wednesday with a cold front associated with the aforementioned Canadian shortwave. The front looks to hang up across the Southern Great Lakes with additional rain into Thursday and perhaps Friday. The item of note here is that moisture in the mid and upper levels, associated with what will be former Hurricane Polo, could potentially interact with the front in the Southern Great Lakes during this time frame. PWATs are forecast by the GFS to reach 2.00 inches which is very high/record for late Sept/early Oct. It is a long way out on day 5 and 6 so we have time to watch it, but it has our attention. Heavy rain events of the past have had similar setups with remnant moisture streaming northward from former tropical systems. One event that comes to mind is September of 2008 when moisture from Gustav, Lowell and Ike all made it`s way north into Lower Michigan. We are not by any means saying we are looking at an event like that, but some heavy rain is possible this upcoming week. 1-2 inches of rain seems plausible. Individual ensemble members are indicating higher than that. - Above normal temperatures expected Normal high temperatures this time of year are in the 60s and for much of the 7 day forecast we are looking at highs in the 70s. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 208 AM EDT Sat Sep 26 2026 Mainly VFR weather is expected the next 24 hours. VFR weather is actually what is in all 6 TAFs for the moment. High pressure will bring mainly clear skies and fair weather the next 24 hours. The exception to that rule is the threat of some low clouds developing in a light northeast flow off of Lake Huron. Models are trying to depict low clouds developing between 08z and 12z towards FNT and PTK and drifting towards LAN and JXN. At this point have opted to keep these low clouds out of the TAFs, but we will be monitoring. Winds will be light from the east and northeast at less than 10 knots through the period. && .MARINE... Issued at 350 AM EDT Sat Sep 26 2026 Conditions are expected to remain quiet on the big lake into early next week. A ridge of high pressure will remain situated over the Great Lakes region resulting in light winds and limited wave action. Waves in the next few days will be 2 feet or less and for most of the time less than a foot. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke AVIATION...Duke MARINE...Duke

NWS GRR Office Area Forecast Discussion