672 FXUS63 KGRR 242240 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 640 PM EDT Thu Sep 24 2026 .KEY MESSAGES... - Dry and mild through the weekend - Chance of rain late Tuesday/Wednesday && .DISCUSSION... Issued at 126 PM EDT Thu Sep 24 2026 - Dry and mild through the weekend The blocking ridge over Ontario/Quebec continues to dominate our weather and will through the weekend. Latest visible loop shows clear skies over much of the cwa with some diurnal co over the southern row...around the periphery of the Ohio Valley low. We aren`t going to see much change for several more days as the blocking pattern remains in place. Highs from the mid 60s to lower 70s Friday will gradually warm to highs in the lower to mid 70s by Monday. Lows in the mid to upper 40s are expected each day. - Chance of rain late Tuesday/Wednesday The GFS has taken a turn toward the ECMWF late Tuesday and Wednesday and now shows a northern stream wave moving across the upper Midwest and knocking down the ridge. Concurrently, a southern stream wave helps to develop a surface low in the southern Plains. This result is that the cold front pushed across the state by the northern wave gets hung up over the cwa late Tuesday into Wednesday by the developing Plains low. This frontal boundary then becomes quasi stationary and a focus for shower development. Thus, confidence is fairly high that we`ll see precipitation late Tuesday into Wednesday that may linger into Thursday. ECMWF and GFS ensembles also show this. At this point, the thunder threat looks low given weak instability. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 639 PM EDT Thu Sep 24 2026 Clear skies are expected this evening before a widespread cirrus deck visible on satellite moves across the terminals overnight. Cigs will remain VFR, in the 15-20kft range. This should limit radiational cooling and limit fog development, but there is still a 10-15% chance of MVFR conditions according to the latest probabilistic guidance. Skies clear out near the end of the TAF period. Othwewise, expect east to northeast winds below 10 knots. Muskegon is favored to see winds shift to north or northwesterly late in the TAF period thanks to a lake breeze. && .MARINE... Issued at 126 PM EDT Thu Sep 24 2026 A high pressure ridge over the Great Lakes will continue to supply the region with an easterly wind flow. That will push the highest waves off shore. Given the light pressure gradient, even the waves at the 5 mile point off shore will be at or below 3 feet. These conditions will persist through the weekend. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...04 AVIATION...Thomas MARINE...04

NWS GRR Office Area Forecast Discussion