348 FXUS63 KGRR 102255 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 655 PM EDT Fri Jul 10 2026 .KEY MESSAGES... - Lingering Convection across the Southeast - Upper High builds in early next week - Storminess possible latter half of next week && .DISCUSSION... Issued at 300 PM EDT Fri Jul 10 2026 - Lingering Convection across the Southeast Convergence along and ahead of a surface cold front, along with diurnal peak heating and resulting instability, will yield scattered thunderstorms across the southeast quarter of the forecast area through early evening. Sfc-based CAPE around 1000 J/kg will persist in that area into the evening along with 25 to 30 knots of deep layer shear, so a few organized, persistent updrafts are possible and some could produce localized downbursts similar to those observed yesterday. Drier and cooler air advects in later this evening, putting an end to the storms after sunset. - Upper High builds in early next week Drying and subsidence will rule over the weekend and into next week. A heat dome over the PLains/Upper Midwest builds into Lower Michigan, peaking on Tuesday before heights fall as upper troughing amplifies across eastern Canada. Although thermal profile forecast tools suggest mid 90s are possible on Tuesday, the current forecast apparent temperatures do not reach the local Heat Advisory criteria of 100F. This is mainly due to forecast dew point temperatures not reaching 70 degrees. Recall that dew points were in the mid and upper 70s during the hot weather at the beginning of the month. So this will be a comparatively "dry heat". - Storminess possible latter half of next week The models have come into better agreement on the development of a deep upper trough across eastern Canada next week. Heights fall as the upper high retreats westward beginning Wednesday with cooler temperatures along with the possibility of ridge-riding convection Thursday and beyond. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 642 PM EDT Fri Jul 10 2026 VFR will dominate the pattern over the next 24 hours. The caveats are twofold. First, convection that forms through our far SE zones this evening. There is a low probability of showers/storms in and around JXN between 00Z and 02Z. Second, patchy fog/mist that could reduce vsbys to MVFR, mainly JXN. && .MARINE... Issued at 300 PM EDT Fri Jul 10 2026 North winds will gust to near 20 knots this evening as high pressure builds in and then decrease after midnight. Winds go more northeast and offshore later tonight and Saturday generally less than 15 knots. Wave action will be minimal until early next week when southwest winds increase to near 20 knots. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...Ceru MARINE...Ostuno

NWS GRR Office Area Forecast Discussion