189 FXUS63 KGRR 161728 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 128 PM EDT Sun Aug 16 2026 .KEY MESSAGES... - Scattered showers and storms today - Shower/storm chances late Tue to early Wed, and late week && .DISCUSSION... Issued at 321 AM EDT Sun Aug 16 2026 - Scattered showers and storms today Scattered showers and thunderstorms are expected in the vicinity of an MCV moving from northern Illinois to southern Michigan this morning, then ahead of a weak cold front sweeping through the state this afternoon. CAPE values 500-1000 J/kg are confined mainly south of I-96 this morning, though may extend farther north for a time around mid day. Storm cells should be fairly limited in organization given about 20 knots of 0-6 km shear. PW around 2 inches will make for efficient rainfall rates, though limited updraft width and scattered coverage of cells would favor just isolated spots of 1-2 inch totals, highest probability south of I-96 per the HREF. - Shower/storm chances late Tue to early Wed, and late week Monday will bring relief from the humidity, as dew points drop to around or below 60. Some moisture and slightly warmer air from the central CONUS returns on Tuesday, ahead of a cold front that will sag through on Wednesday, nudged south as an upper-level low lumbers across Hudson Bay and northern Ontario. Scattered thunderstorms are again possible in the vicinity of this front mainly between Tue evening and early Wed morning, as a majority of ENS and GEFS members indicate. Instability is still a little in question, as most solutions project fairly modest amounts in the ballpark of 500-1000 J/kg, though a few offer closer to 2000 J/kg. This would be something to monitor for a marginal severe threat, as deep-layer shear will be greater than it is today. A majority of ensemble member solutions favor drier and somewhat cooler air for later Wed into Thursday, followed by another modest moisture return late Friday into Saturday with a chance for more scattered showers or storms. Naturally, this is lower confidence this far out, given the increasing spread in the solution envelope. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 127 PM EDT Sun Aug 16 2026 Light rain has ended across the region and skies are beginning to clear. Still some IFR ceilings out there but gradual improvement is expected through the early overnight. As morning approaches, we`ll see some IFR fog develop, but that will burn off by mid morning as we head toward VFR conditions late in the period. && .MARINE... Issued at 1053 AM EDT Sun Aug 16 2026 Trapped moisture aided by recent rainfall and humidity has cause dense fog along the lakeshore this morning. Winds remain fairly light so expecting this fog to continue through at least the first half of the afternoon until the winds shift when the cold front comes through. Southwest winds become west today then north tonight. A few thunderstorm cells are possible over Lake Michigan this morning, mainly an occasional lightning threat. Waves will be 1 to 2 feet with a low swim risk today. The north winds should kick up 2 to 3 foot waves tonight. A low swim risk is expected Monday, then a moderate swim risk Tuesday with southwest winds. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Dense Fog Advisory until 6 PM EDT this evening for LMZ845>849. && $$ DISCUSSION...CAS AVIATION...04 MARINE...CAS/Ceru

NWS GRR Office Area Forecast Discussion