677 FXUS63 KGRR 120417 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1117 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 /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1111 PM EST Thu Dec 11 2025 Skies are overcast across the terminal with ceilings ranging from MVFR to VFR. Forecast soundings overnight show a pronounced inversion overnight across the region. That will trap low level moisture in place and not allow ceilings to fluctuate much. The exception to that might be at LAN/JXN where some clearing skies across the Thumb and northeast Lower are trying to move southwest a bit. The higher likelihood is that skies will remain overcast and that is the direction that the TAFs lean. An Arctic cold front will move across the terminals Friday evening and light snow will accompany the front. Ceilings/visibilities will fall to MVFR after 00z as the front moves through. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ostuno AVIATION...04

NWS GRR Office Area Forecast Discussion