859 FXUS63 KGRR 112236 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 536 PM EST Thu Dec 11 2025 .KEY MESSAGES... - Lake Effect Snow Friday and Saturday - Arctic Air into Early Next Week && .DISCUSSION... Issued at 315 PM EST Thu Dec 11 2025 - Lake Effect Snow Friday into Saturday Inversion heights lower tonight as surface ridging with subsidence and drying builds in, ending the snow showers except in the far NW zones. Some clearing is possible inland which would allow temperatures to drop below 10F and possibly below zero if skies remain clear for several hours. An a shortwave trough arrives Friday afternoon and raises inversion heights to around 10 kft. We expect lake effect snow to perk up in southwest to west flow during the afternoon. There could be a brief burst of heavier snow as an arctic front moves though Friday evening with strong low level convergence with lake effect continuing in west-norrthwest flow behind the front. Given onshore flow and strong lake instability, we expect some localized amounts of 3 to 5 inches of snow before inversion heights fall and snow showers decrease on Saturday. - Arctic Air into Early Next Week A vast area of arctic air pooling across northwest Canada surges southeast by the weekend, with a lobe of the polar vortex reaching Lower Michigan by Sunday. 850 MB temperatures plunge below minus 20C and should result in high temperatures being confined to the teens on Saturday and Sunday with wind chills approaching minus 10F, especially Saturday night when the core of the coldest air aloft comes through. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 536 PM EST Thu Dec 11 2025 TAF sites should climb VFR cigs at or shortly after 00z and remain there through at least 04z. Uncertainty increases after 04-06z with two main scenarios possible based on model guidance. First (and more likely) is that the robust cloud deck holds, possibly lowering to MVFR with weak subsidence and a lack of notable thermal advection to break the inversion. Second (lower confidence) is that breaks in the clouds allow FZFG to form with visibility restrictions thanks to moisture from the robust snowpack. Have favored scenario one in the 00z TAF package given the aforementioned factors leading to questions on if we can break up the stratocu. However, satellite trends will need to be watched closely to see if trends towards clearing skies and FZFG materialize. Either way, improvement to solid VFR is likely by late Friday morning/early Friday afternoon. Snow then arrives from the west near to after 00z, with MVFR conditions possible in any snow. Low chances at GRR/MKG in the late TAF period warrant a PROB30 with higher confidence in snow timing after 00z. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...Thomas

NWS GRR Office Area Forecast Discussion