969 FXUS63 KGRB 310447 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1047 PM CST Tue Dec 30 2025 Updated aviation portion for 06Z TAF issuance .UPDATE... Issued at 811 PM CST Tue Dec 30 2025 Widespread snow is shutting down over central Wisconsin, but radar and obs show the snow is continuing over eastern WI, including the Fox Valley. Snow has been quite fluffy and efficient with SLRs over 20:1 the entire time. Snow amounts over 3 inches were reported in southern Winnebago County this evening. As of 6pm, we had nearly 2 inches at our office near the Green Bay airport. Back edge of snow is pressing east-southeast and will reach the Fox Valley by 10p. Heavier radar echoes over 20dbz suggesting snowfall rates of at least 0.5"/hr have faded over the last 2 hours. Other aspect of this system has been some freezing drizzle that for the most part has remained southwest of central Wisconsin. Could see a bit of freezing drizzle as the snow ends late this evening, especially south of highway 10. Another wave of light freezing drizzle has developed upstream northeast MN into the Duluth vicinity, now pushing into northwest WI. Not sure if this will hold together as it slides into central WI, but enough evidence upstream to add a mention overnight across central WI and perhaps reaching the southern portions of the Fox Valley late tonight. Confidence on how the freezing drizzle evolves overnight is low. && .KEY MESSAGES... - A clipper system brings a round of fluffy snow through this evening. An inch or less is likely for most, with 1 to 2 inches expected in the Fox Valley, bayshore and lakeshore areas as well as across the lake effect snow belt in north-central Wisconsin. Minor travel concerns are expected. - An arctic cold front will bring additional light snow on Wednesday, with a dusting to a half inch anticipated in most areas. A couple inches of snow will be possible in Vilas County due to lake-effect. - Wind chills as cold as 15 to 25 below zero are possible New Years Eve night into the morning on New Years Day. && .DISCUSSION... Issued at 210 PM CST Tue Dec 30 2025 First Round of Snow: A fast moving Clipper system is currently bringing a swath of light snow and flurries to the region late this afternoon. Although moisture is meager, snow ratios are fairly high (upper teens) with fairly good dynamics in the form of a mid level PV anomaly and left-front quad of a 110 knot upper level jet. The high snow ratios and dynamics should lend themselves to most areas getting around a half inch of snow, with the Fox Valley, bayshore and lakeshore areas could get 1 to 2 inches. This will produce slick roads, especially in eastern Wisconsin, for the evening commute. Arctic Cold Front Snow: An arctic cold front will move into northern Wisconsin late tonight, then drop south through the rest of the region during the day on Wednesday. As this occurs, conditions will become more favorable for lake-effect snow (northwest winds and increasing instability over western Lake Superior with delta T values around 20) in north-central Wisconsin, with accumulations of 1 to 3 inches possible in Vilas County. Despite the arrival of a dry arctic air mass, will keep POPs higher than NBM (30-50%) given fairly strong dynamics with the frontal passage, increasing frontogenesis, a mid-level short- wave and the left-front quad of a 135 kt jet streak. Outside of the lake-effect region, only expecting a dusting to a half inch of powder in most areas. Brief Period of Cold: A fairly strong push of cold air arrives in the wake of the arctic front, with 800 mb temperatures dropping to 18 to 23 below zero Celsius across the region later Wednesday into Wednesday night. The combination of surface temperatures falling into the single digits below zero (except near Lake Michigan) and persistent northwest winds will result in wind chills of 15 to 25 below zero late Wednesday night into Thursday morning. These cold temperatures would likely impact any activities late New Years Eve into the morning hours of New Years Day. Cold Weather Advisories may eventually be needed for roughly the northwest half of the forecast area. Some moderation in temperatures is expected Thursday into Thursday night as incoming cloud cover prevents temperatures from tanking overnight, which will mean wind chill values will only fall to around 10 below zero across central and north-central Wisconsin Thursday night into Friday morning. Rest of the Forecast: No significant precipitation events are expected for the rest of the extended forecast period. After the brief shot of arctic air, a gradual moderate in temperatures is expected, with highs reaching the 20s by Sunday/Monday. && .AVIATION...for 06Z TAF Issuance Issued at 1042 PM CST Tue Dec 30 2025 Light snow has ended over eastern WI. Patchy freezing drizzle could occur over central WI late tonight, but this is a very low chance and will leave out of this set of TAFs. Otherwise, rest of tonight will feature transient clouds with any cigs MVFR to lower VFR. A few flurries may occur at times over far north-central WI. Snow may move back into RHI around daybreak Wednesday as an Arctic front arrives from the north. As the front moves through, another round of light snow (vsby mostly VFR, but as low as MVFR portions of central WI) would occur from mid morning through mid afternoon, before tapering off by late afternoon as the front shifts south. Cigs on Wednesday will be mainly MVFR. Skies clear out by Wednesday evening, except over north-central WI where lake effect clouds and a few flurries will linger. Winds will be from the W-NW with speeds of 10 knots or less the rest of tonight. Northwest winds on Wednesday then increase to 10 to 20 knots as the Arctic front moves through. Winds will diminish late Wednesday evening. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.........JLA DISCUSSION.....Kurimski AVIATION.......JLA