554 FXUS63 KGRR 161153 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 753 AM EDT Sat May 16 2026 .KEY MESSAGES... - Storms this morning - Unsettled into next week; strong/severe storms possible Monday - Cooler mid to late week && .DISCUSSION... Issued at 224 AM EDT Sat May 16 2026 - Storms this morning Regional radar shows a well defined MCV moving ENE across central Wisconsin. A large area of strong to severe storms was noted with this MCV. Dewpoints in Wisconsin are in the mid 50s...10 degrees higher than across the cwa. SPC meso progs suggest that we`ll see 500 or so j/k MUCAPE toward sunrise in southwest Lower. This should result in a weakening trend as the convection pushes across the lake. This convection should move across the lake around 400 am and continue eastward, exiting the cwa around 12z. Latest GFS shows increasing shear between 09-12z suggesting that the storms won`t weaken too quickly despite lower moisture levels. Indeed, latest IR loop continues to show cooling cloud tops to the west. Once the convection moves east of the cwa, there will be a lull. However, a few of the CAMs point toward renewed showers across near I-94 late morning. Then, the rest of the day through mid afternoon Sunday will be dry. - Unsettled into next week; strong/severe storms possible Monday A northward moving warm front will move into Lower MI Sunday afternoon, and this may become a focus for renewed convective development. Dynamics are somewhat weak; shear values are around 20 kts south of I-96, but closer to 35 knots over the northern cwa, which is where the RRFS EMC shows some development. Once the warm front moves north, we`ll be watching trends along the cold front over Wisconsin/Iowa Sunday night into Monday. Strong to severe storms will fire along the front across Wisconsin Sunday night and move east, potentially affecting the northern cwa Monday afternoon with more development farther south along the frontal boundary Monday night. Some of these storms could be strong to severe as well. The convective threat will remain until Tuesday when the cold front will move through. - Cooler mid to late week Air behind the cold front will be in the 60s Wednesday and Thursday...quite a bit cooler than the 80s ahead of it. However, temperatures will warm into the lower to mid 70s Friday and Saturday. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 752 AM EDT Sat May 16 2026 Line of showers and embedded storms that moved through earlier have shifted east of the terminals. We do have some scattered showers with very little to no thunder popping up with the next wave moving toward the area. This will bring a few showers to the terminals through 15-17z before ending. Some spotty MVFR may be possible, with VFR dominating. The rest of the day will see clearing skies and VFR conditions. Winds will be somewhat gusty with gusts 20-25 knots. We will see another chance for some additional showers/ thunderstorms developing. These should mostly be after midnight. Not too confident yet whether each site will see them, so went with prob30 for now. Any storms could bring locally MVFR to IFR conditions. && .MARINE... Issued at 224 AM EDT Sat May 16 2026 A weak pressure gradient will result in little if any marine issues through Sunday. Winds will increase Sunday night as low pressure over the upper Midwest advances eastward; a small craft advisory may be needed Sunday night through Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...04 AVIATION...NJJ MARINE...04

NWS GRR Office Area Forecast Discussion