491 FXUS63 KGRR 250321 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1121 PM EDT Wed Jun 24 2026 .KEY MESSAGES... - Scattered Showers and Thunderstorms Through Thursday - Hot With Thunderstorms Possible Next Week && .DISCUSSION... Issued at 202 PM EDT Wed Jun 24 2026 - Showers and Thunderstorms Through Thursday Radar shows a batch of showers crossing the area this afternoon, with additional development expected this evening. The advection of slightly better mid-level lapse rates across the area this evening will lead to an increase in MUCAPE to 500-1000 J/kg supporting embedded thunder potential. Given a low-level jet impinging on the southwest CWA late this evening cannot completely rule out a strong storm, however confidence is low with limited instability as a significant limiting factor. These storms should wind down by early Thursday morning. There are some signals for additional showers and storms to develop Thursday afternoon with low passage, with the best chance across the northeastern CWA. - Hot With Thunderstorms Possible Next Week Late this week into this weekend will feature a transition into a large scale ridging pattern across the Central and Eastern CONUS. Generally fair weather is expected. 850mb temps are forecast to climb into the 20s C by next week translating into surface temps into the 90s. Given dewpoints in the 70s, this could translate into heat indices into the 100s early next week. This would bring the potential for increased heat related illness/impacts and needs to be closely monitored over the next week. The pattern is favored to continue into the Independence Day weekend. However any thunderstorm activity could impact how hot things get. The other concern is for thunderstorm potential into next week. The hot and humid airmass will lead to significant instability across the area with forecast GFS/ECMWF MUCAPE values north of 2000 J/kg at times. Given our forecast position on the northern periphery of the ridge, and the signal for embedded shortwaves within the large scale pattern, the potential for organized convection across the Great Lakes region exists. However, certainty in where and when any thunderstorms would develop is low given the reliance on small-scale waves in the large scale pattern. Refinement of the forecast is expected as we get closer. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1121 PM EDT Wed Jun 24 2026 Latest radar shows scattered showers and isolated thunderstorms will continue over the next few hours. Have amended the LAN TAF to time thunder through the airport. so far the showers along the I 94 corridor do not have thunder. So while it is possible, will only have PROB30 for that potential. Once these showers move through, around 08Z, Low clouds and fog will develop with IFR conditions favored and pockets of LIFR possible. Any low clouds scatter out by late morning Thursday given strong June sunshine. Shower and thunderstorm development Thursday afternoon is expected to focus north and east of the terminals. && .MARINE... Issued at 344 PM EDT Wed Jun 24 2026 Observations from the Port Sheldon buoy currently have south winds around 17 knots gusting to 23, a significant wave height of 3.4 feet, 10th percentile wave height of 4.4 feet, and maximum wave height of 5.4 feet. This moderate to high swim risk will continue into this evening for Port Sheldon and Grand Haven and north toward Ludington, with the south side of south piers having the most dangerous currents and largest waves. High pressure then arrives later Thursday into Friday causing winds and waves to subside. Showers are likely with thunderstorms possible this afternoon and evening across the waters. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Thomas AVIATION...Ceru MARINE...CAS/Thomas

NWS GRR Office Area Forecast Discussion