833 FXUS63 KGRR 240037 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 837 PM EDT Fri Oct 23 2026 .KEY MESSAGES... - Dense Fog Saturday Morning; Patchy Fog on Sunday - Pattern Change ahead with chances for rain beyond midweek && .UPDATE... Issued at 836 PM EDT Fri Oct 23 2026 Main concern this evening continues to be fog potential into the overnight hours. Southeast flow is forecast to enhance low-level moisture off of Lake Erie with light winds which is favorable for fog formation like last night. One caveat is there will be some high clouds in play, though with hybrid advection fog scenarios like this that`s not always a deterrent. Forecast soundings are favorable with moisture trapped under a strong low-level inversion. Dense fog is possible areawide, with two areas in particular worth monitoring. The first is from JXN northeast into LAN and GRR where the best trajectory of moisture off of Lake Erie is. The other is the lakeshore north of MKG where southwest winds have led to some localized fog enhancement the last few nights and LDM`s observation suggests may be underway again tonight. Any fog that develops is likely to be slow to mix out given lower sun angles this time of year, potentially lingering into mid morning. && .DISCUSSION... Issued at 157 PM EDT Fri Oct 23 2026 - Dense Fog Saturday Morning; Patchy Fog on Sunday High pressure will continue dominate the weather pattern with light winds and warmer air through the weekend. The light winds, high pressure, clearing skies is a great recipe for morning fog. There is some question if it forms later. However, the flow from the east should allow for moisture to converge overnight and fog to form across the region. Models remain consistent with highs 10 to 15 degrees above normal with Max temps in the upper 60s to low 70s across the lower Peninsula. The flow will shift Saturday night into Sunday and this will lessen the chance for fog development. However, given radiational cooling, clearing skies and light winds overall, patchy fog will be again possible Sunday morning, though it should be less dense than Friday and Saturday. - Pattern Change ahead with chances for rain beyond midweek The upper level pattern has the high shifting southward and flattening next week. However, sfc high pressure should remain stout enough to keep any moisture bands to only effect the northern half of the lower Peninsula Monday and Tuesday. The ensembles diverge on timing but the cold front associated with a low pressure system tracking from the Canadian Rockies to Hudson Bay will likely bring cooler air into Michigan dropping highs closer to normal, in the upper 50s to mid 60s. Warm air advection midweek will correspond with a deepening trough that will swing through the region and is the next chance showers. Pwats are potent so about a quarter inch of rainfall is possible. Models continue to diverge after in the movement, timing and postilion of the upper level pattern. So a continued low confidence in the forecast for the end of next week. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 723 PM EDT Fri Oct 23 2026 VFR conditions are expected at the beginning of the period, but another round of fog is expected overnight through tomorrow morning across much of lower Michigan. Highest probabilities of LIFR ceilings and visibilities are at LAN and JXN, followed closely by GRR and MKG. Confidence is low that fog will develop at BTL and AZO, as fog did not develop there the previous night, and model probabilities are much lower west of US-131. Fog should linger through mid morning, with VFR conditions thereafter. BRC && .MARINE... Issued at 157 PM EDT Fri Oct 23 2026 Fair winds and waves will dominate the pattern today. Another round of fog will be possible Saturday and Sunday morning and may affect the harbors and portions of the nearshore, mainly north of Grand Haven. Southerly winds will increase tomorrow, upwards of 10 to 20 kts and will build waves to 2 to 4 feet north of Whitehall, persisting into Sunday morning. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...Thomas DISCUSSION...Ceru AVIATION...BRC MARINE...Ceru

NWS GRR Office Area Forecast Discussion