FXUS63 KGRR 081741 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 141 PM EDT Wed Jul 8 2026 .KEY MESSAGES... - Scattered Showers and Storms This Evening Through Thursday - Mostly Dry Weekend Favored and Heating Back Up && .DISCUSSION... Issued at 327 AM EDT Wed Jul 8 2026 - Scattered Showers and Storms This Evening Through Thursday Overall a decent signal for a few rounds of scattered thunderstorms between late this evening and late Thursday, but fairly unimpressive environment and dynamics that will keep details of predictability low (when and where exactly it will storm) low and also cap potential at just a marginal threat of wind/hail. But the confidence is fair via the HREF for three main windows for storms: late evening weakening storms crossing the lake toward areas north and west of Grand Rapids, then some elevated Thu morning thunderstorms in west-central and central Michigan, then more surface-based storms Thu afternoon east of US-131. Also early this afternoon, can't rule out a weakening thunderstorm surviving into Ludington. Much about this setup is on the positive but weak side for supporting storms: the sagging cold front, the upper-level jet dynamics, the moistening low-levels and 850 mb moisture transport, the cooling mid-upper levels that will yield about 500-1000 J/kg of CAPE (perhaps more Thu afternoon), and about 20 knots of deep- layer shear. Despite the midlevelds also expected to be rather moist, the well mixed lower atmosphere both this evening and Thu afternoon should support about 500 J/kg of DCAPE per the HRRR, allowing for a chance for a coalesced cold pool to sweep into West Michigan this evening with 30-40 mph gusts, then isolated near- severe wind gusts in mid/southern Michigan Thu afternoon. - Mostly Dry Weekend Favored and Heating Back Up PoPs are about 10 percent through the weekend as upper level ridging and surface high pressure is most favored over Lower Michigan. A heat wave is expected to develop this weekend to early next week from the Intermountain West into the Northern Plains, with 500 mb heights potentially reaching 600 dekameters over the Dakotas on Monday per the ECE. This plume of 21-24 C air at 850 mb may advect into Michigan from the west-northwest, making highs in the 90s possible Mon to Tue/Wed. The ECE and CMC are the most aggressive with the heat, and GEFS a little less but still quite warm. Dew points may be in the mid 60s this time, less humid than last week's heat wave. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 141 PM EDT Wed Jul 8 2026 The ongoing cluster of storms over Central Lake Michigan is forecast to move just south of MKG. Otherwise, thunderstorms from Wisconsin look to arrive after 02z across Central Michigan. Impacts to GRR/MKG remain low in confidence so will maintain existing PROB30s. Scattered showers and storms then continue overnight mainly north of GRR/MKG/LAN with greater coverage possible later Thursday morning. There's a signal for a line of storms to develop near JXN/LAN after 15z, which given lwo confidence have included PROB30s for now. Any storms may contain brief increases in wind and wind shifts. Otherwise expect mainly west or southwest winds aob 10 knots. && .MARINE... Issued at 327 AM EDT Wed Jul 8 2026 Winds over the water will mostly be from the south-southwest 5 to 15 knots today, though weakening showers or thunderstorms crossing the lake this afternoon and/or evening may cause shifting winds to west/northwest and gusts 20-30 knots or perhaps stronger. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert until midnight EDT tonight for MIZ050-056-057- 064-065-071. MARINE...None. && $$ DISCUSSION...CAS AVIATION...Thomas MARINE...CAS