152 FXUS63 KGRR 150600 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 200 AM EDT Sat Aug 15 2026 .KEY MESSAGES... - Showers and Storms Saturday into Sunday - Cool and Dry through beginning of the week - Showers and storms possible mid next week && .DISCUSSION... Issued at 306 PM EDT Fri Aug 14 2026 - Showers and Storms Saturday into Sunday There have been some shifts in the trends for tomorrow`s incoming system. Today, the showers and storms continue to stream through Illinois and Indiana. This trend was expected to shift northward but there is some question to what extent. An upper level vort max is still shown to move through Lower Michigan tomorrow, This would create some afternoon into early evening convection along and southward of the I 94 corridor. This is highlighted in the SPC Day 2 convective outlook. Latest Model soundings through the Kalamazoo region so lapse rates only 5 to 6 C/km with a mid level inversion tomorrow that could stifle any convection. Some of the ensembles do show some weak shear Saturday evening that shifts to the north and could allow some showers and storms along the I 96 corridor Saturday evening. So scattered showers and storms are possible, there is the possibility any convection remains to the south. The overall trend continues to show a shift of stronger convection southward. There remains a chance for increased precipitation through the south and given the moisture aloft, any showers could by heavy, with QPF of over an inch of rain possible. There is a deeper upper level trough with mid level support moving through early Sunday. While there is less moisture with that system and it comes in overnight into early Sunday, it currently has the better CAPE and shear. While not huge, there is 1500 J/kg of MU cape and Lapse rates towards 7 C/km. This is with the frontal boundary and propagates through between 15Z to 21Z Sunday. So there remains a multitude of questions with the systems this weekend, there remains several chances for showers and storms across lower Michigan until Sunday evening but the trend shows a lower potential. - Cool and Dry through beginning of the week There is good consistency that this front moves through Sunday night with drier, cooler northwesterly flow into Monday. A large upper level low over Canada will dominate the pattern through the next week. It should form into a closed low over Hudson Bay through mid week. This will keep temps at to below normal with the region dry. - Showers and storms possible mid next week The previously mentioned upper level low will drive a short wave trough through the region and a corresponding low through the Great Lakes midweek. Currently there should be an elongating front associated with with warm air advection out ahead of it. There remains some position and timing questions. It could remain further north and/or come in later. But Wednesday into Thursday could see some decent convection. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 200 AM EDT Sat Aug 15 2026 Generally less favorable flight conditions are expected in southern Michigan and better conditions in central, while aerodromes such as MKG, GRR, and LAN may experience more of a mix of conditions. The onset of worsening flight categories is rather low confidence in timing as models have not been handling the weakly forced showers well so far, and later shower development on Saturday is also expected to be weakly forced. It is possible that these TAFs are too optimistic, and temporary IFR visibility may occur today under moderate rain showers, and patchy MVFR ceilings may develop as the lower atmosphere moistens inconsistently. && .MARINE... Issued at 303 PM EDT Fri Aug 14 2026 The only marine concern is the potential for showers and storms Saturday through Sunday. Flow should remain offshore with a wind shift into Sunday. There is an increase in winds/waves Saturday night into Sunday. However, the gradient doesn`t seem to support any winds/waves that would reach criteria. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ceru AVIATION...CAS MARINE...Ceru

NWS GRR Office Area Forecast Discussion