943 FXUS63 KGRR 201035 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 635 AM EDT Thu Aug 20 2026 .KEY MESSAGES... - Dry and less humid today - Showers with some thunderstorms Friday into the weekend && .DISCUSSION... Issued at 240 AM EDT Thu Aug 20 2026 - Dry and less humid today Today should feature dewpoints ranging from the upper 40s over central interior Lower Michigan to the upper 50s farther south along the I-94 corridor. This will feel noticeably drier to many. Maximum temperatures will range from near 80 to the lower 80s, with maximum apparent temperatures about the same or even slightly less where dewpoints are lower. Another and more robust measure of potential heat stress, known as the WetBulb Globe Temperature (WBGT), gives a reading of lower 70s for this afternoon. So all of this is to say that it should feel relatively comfortable outside today. - Showers with some thunderstorms Friday into the weekend Certainty is growing that we will see showers and thunderstorms moving through the forecast area Friday night and exiting to the east of the area by Saturday afternoon, yielding a dry Sunday. The exception may be the immediate lakeshore, particularly the Sable Points area, where lower tropospheric cooling may be sufficient for lake effect sprinkles. The growing certainty is related to the most recently available ensemble guidance, which shows a mean solution of meridionally deeper upper troughing that`s particularly pronounced into the Ohio Valley region. The expectation still is that this trough will become a cutoff low centered somewhere over the north-central Great Lakes region. The more amplified solution at this location means more of an equatorward component of the flow aloft over Lower MI, which is a drier pattern and suggests precipitation will remain shunted east of our forecast area after Saturday afternoon. However, it should be noted that ensemble solutions from as recently as yesterday morning and afternoon showed a sizable number of members forecasting precipitation through Sunday. So, although there is growing confidence for a dry Sunday, this is far from certain. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 635 AM EDT Thu Aug 20 2026 No significant changes were made for this update. It appears that there is enough low level dry advection even at our southern terminals to remove the threat of any fog this morning, as the previously mentioned boundary with elevated RH had moved south of the area. There are broken cloud layers ranging between 4500-6500 ft AGL that are being reported primarily across southeastern Lower MI and affecting our easternmost terminals (LAN and JXN). However, these clouds are expected to dissipate or move out of the area. After this, scattered cumulus with bases 3500 feet AGL or greater are expected to develop by late morning or early afternoon with a very high probability (95 percent chance) of VFR conditions continuing through at least 00Z at all of the terminals. && .MARINE... Issued at 240 AM EDT Thu Aug 20 2026 No concerns in the short term. Winds and waves could meet Small Craft Advisory thresholds by Friday afternoon, mostly around the Sable Points, due to persistent and moderately strong winds from the south-southwest over Lake Michigan. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...TJT AVIATION...TJT MARINE...TJT

NWS GRR Office Area Forecast Discussion