135 FXUS63 KGRR 022308 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 708 PM EDT Sun Aug 2 2026 .KEY MESSAGES... - Isolated showers this afternoon, then dry through late Tuesday - Showers and storms possible from Wednesday through the weekend && .DISCUSSION... Issued at 214 PM EDT Sun Aug 2 2026 - Isolated showers this afternoon, then dry through late Tuesday The larger area of deformation zone precipitation has exited the forecast area. Radar shows isolated showers across the eastern CWA moving southwest, mainly around US-127. Some model guidance, particularly the NBM, favors thunder this afternoon with this activity in the Lansing area. Given limited conditional instability that is mostly below the ice production layer, we feel that thunder is quite unlikely, but admittedly non-zero, with this activity. After this, forecast expectations have really not changed for the week ahead. There is a signal for some Monday morning shallow ground fog, particularly towards I-94. Otherwise, Monday through Tuesday afternoon feature a high certainty (greater than 90 percent) of dry conditions across southwest Lower MI with seasonal temperatures and humidities. Model guidance run to run consistency has been decent with respect to bringing precipitation chances to at least the northwest forecast area (including Ludington) Tuesday night. Accordingly, the latest available SPC SWODY3 brings a general thunder threat to the extreme northwest CWA during this timeframe. - Showers and storms possible from Wednesday through the weekend As previously noted, we will remain in a persistent broad upper trough pattern starting the middle of the coming week and lasting through the weekend. Guidance is locking into a slow cold frontal passage Wednesday into Thursday with attendant showers and thunderstorms. Neither SPC nor Machine Learning (ML) guidance indicate much of a severe threat with this activity. We are going with a possible dry period Friday in the deterministic forecast, but this may be a bit misleading given that numerous members from the ECMWF/GEFS/GEPS model suites give at least a smattering of precipitation every day into early next week. The ensemble guidance output really speaks to the poor timing and magnitude predictability of this pattern given that episodic rainfall will depend greatly on the evolution of meso-alpha scale upper PV maxima moving through the broader cyclonic flow. In terms of severe convective threats after Thursday, the ML guidance is not as bullish as before. This makes sense given that we are looking at an unsettled pattern that will probably be unable to develop significant conditional instability. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 708 PM EDT Sun Aug 2 2026 Scattered light rain showers will gradually dissipate with the fading evening warmth. Scattered VFR cloud bases prevail. There are some lake-induced IFR ceilings reported near Lake Michigan at and southwest of South Haven (LWA). MVFR ceilings are streaming off Saginaw Bay near MBS, a few of those clouds are close to reaching LAN. Fog potential late tonight will be the next challenge, as it`s currently not high confidence. High-resolution models are not big on a fog signal tonight and have 10-15 knot winds several hundred feet above the ground, but our forecast low temperatures are several degrees below the crossover temperature. At least some patchy or shallow fog would be possible prior to 11 Z. && .MARINE... Issued at 214 PM EDT Sun Aug 2 2026 No changes to the marine headlines or to expectations in general. We expect an increase in winds and waves this afternoon with dangerous longshore currents that will be especially hazardous on the north sides of structures such as piers. Conditions should improve overnight. The next chance for hazardous winds and waves appears to be Tuesday afternoon farther north around the Sable Points. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until 2 AM EDT Monday for MIZ037-043-050- 056-064-071. MARINE...Small Craft Advisory until 2 AM EDT Monday for LMZ844>849. && $$ DISCUSSION...TJT AVIATION...CAS MARINE...TJT

NWS GRR Office Area Forecast Discussion