659 FXUS63 KGRR 112242 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 642 PM EDT Sat Jul 11 2026 .KEY MESSAGES... - Possible Heat Wave Through First Half of the Week - Mostly Dry through the week && .DISCUSSION... Issued at 245 PM EDT Sat Jul 11 2026 - Possible Heat Wave Through First Half of the Week Bottom Line upfront: Potential to reach heat advisory values through first half of next week. An Upper level ridge emanating from a high pressure system over the Great Plains will continue to build through Canada through the first half of the week. That high will dominate the weather pattern with only minor changes to the forecast. The Max temperatures continue to be forecasted into the mid to upper 90s with the hottest readings on Tuesday. Max temperatures on track to be 10 to 20 degrees above normal. That heat will continue through Wednesday before a large upper level low tracks southward and shifts flow Thursday. The latest ensembles are showing a trend for slightly higher dewpoints Tuesday and Wednesday. NAEFS and EC Ensemble Means are now showing anomalous moisture advecting into the region, especially compared to M Climate. The moisture anomalies are not as robust as our last heat wave. However, the dewpoints could reach into the low 70s Tuesday and Wednesday afternoon. Given that trend, there is the potential for reaching advisory criteria Tuesday and Wednesday with the highest readings possible on Tuesday. - Mostly Dry through the week The upper level ridge as stated above will keep Lower Michigan dry through Wednesday. A low that treks southward late in the week will bring Michigan the next chance for precipitation. There is some question on timing and position but given the day time heating and moisture advection showers and storms are possible through the latter half of the week. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 642 PM EDT Sat Jul 11 2026 High confidence in VFR over the next 24 hours as high pressure and a dry airmass take hold over the area. Diurnal Cu in the 4-6 kft range this evening will diminish shortly after sunset. Northeast winds of 3-8 knots are expected through the TAF period with the exception of MKG. A lake breeze is expected to develop around 16z at MKG continuing through the end of the TAF period causing winds to become westerly. && .MARINE... Issued at 245 PM EDT Sat Jul 11 2026 While there is some concern for northerly flow to pick up this afternoon there is a downward trend. So gusts may approach small craft criteria, however probabilities are low enough to hold off on any headlines. Waves will be highest south of Muskegon with the north sides of piers having the best chance for higher waves, around 3 feet at most given webcams, readings and models. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ceru AVIATION...Thomas MARINE...Ceru

NWS GRR Office Area Forecast Discussion