FXUS63 KGRR 090750 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 350 AM EDT Thu Jul 9 2026 .KEY MESSAGES... - Scattered Showers and Storms Today - Mostly Dry Weekend Favored and Heating Back Up && .DISCUSSION... Issued at 350 AM EDT Thu Jul 9 2026 - Scattered Showers and Storms Today Scattered showers and thunderstorms remain the mode today. While not as warm as yesterday, the humidity will be a little higher. A weak cold front slowly arriving from the northwest, weak midlevel shortwave troughing, and remnant vorticity maxima from yesterday evening's convection over the Upper Miss. River valley, should serve to initiate shower and storm development. Initially elevated convection is possible most anywhere later this morning, then more surface-based storms would be favored east of US-131 during the afternoon. CAPE should be in the range of 750-1500 J/kg. Low-level wind shear is expected to be weak, and deep layer shear of 20 kt is also on the marginal side. With weak forcing and weak storm- relative inflow, storm updrafts should be smaller-scale and less likely to produce severe hail. By afternoon, the well mixed lower levels and DCAPE around 600 J/kg would support locally gusty winds under any of the more robust storm cells, with a marginal risk of severe winds near and east of Battle Creek - Lansing. Rain today is not guaranteed in any location. However, an isolated inch or more of rain could fall in a couple spots. Added patchy fog into the forecast for early Friday morning as winds go calm and skies partially clear. Isolated showers or storms may continue to percolate in mid/southern Lower Michigan tonight into Friday. - Mostly Dry Weekend Favored and Heating Back Up Rising heights in the upper levels and a strengthening surface high over Lower Michigan this weekend will favor a dry forecast. There is about a 10 percent chance of a shower or storm popping up on Sunday, better chances north. As a 500 mb high (associated with a heat wave out west) strengthens and migrates from the SW CONUS to the Dakotas this weekend into Monday, a plume of 20-25 C air at 850 mb will advect into Michigan from the west-northwest Monday-Tuesday. High temperatures in the 90s away from Lake Michigan are well supported by the ECE and GEPS. Dew points may be a little lower than with last week's heat wave, but a heat index in the mid to upper 90s is favored. Mid to late week, the spread in solutions increases (and confidence decreases), dependent on the relative strength and position of the central CONUS high and the eastern Canadian trough, but now a majority of ECE members and about 25 percent of GEPS members (not to mention a few GEFS members) keep highs in the 90s through Friday. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 157 AM EDT Thu Jul 9 2026 Thunderstorm and rain vicinity and north of MKG is gradually weakening and will probably only be a factor distant north of GRR and LAN the next few hours. Expecting cloud bases mostly at or above 4,000 feet today. The big caveat to the prevailing VFR will be scattered showers and thunderstorms developing during the day and moving east. Went with a pretty long duration window of prob30 thunderstorm as models offer a wide variety of solutions regarding coverage and location of thunderstorms at a given time. Any better-developed thunderstorm cells this afternoon, especially east of GRR-AZO, will be capable of microbursts/LLWS and temporary IFR visibility. && .MARINE... Issued at 350 AM EDT Thu Jul 9 2026 Light winds and low waves expected over Lake Michigan today, with wind direction variable depending on location. Can't rule out an isolated thunderstorm developing over the lake this morning. Friday, north-northwest winds may build 2 to4 foot waves and a moderate swim risk by late afternoon. Swim risk is expected to be low this weekend with a high pressure system over the area. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...CAS AVIATION...CAS MARINE...CAS