Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 316 AM EST Wed Jan 22 2025 Valid 12Z Wed Jan 22 2025 - 12Z Sat Jan 25 2025 ...Great Lakes... Days 1-2... The lake effect snow (LES) machine will continue for one more day across the upper Great Lakes while the wind shifts out of the SW over the eastern Great Lakes lead to the single bands off Lakes Ontario and Erie tapering off. A clipper system tracking through Lake Superior today will lead to modest WAA over Lakes Superior and Michigan that, thanks in large part to the air-mass still remaining plenty cold throughout the depth of the troposphere, will support periods of snow through this evening. Cyclonic flow will persist in wake of the weakening clipper system on Thursday which may trigger a few LES bands off Lakes Superior and Michigan. This keeps snow showers in the forecast on Thursday, but snow should taper off by Friday as high pressure builds in throughout the region. WPC 2-day probabilities showed moderate chances (40-60%) for snowfall >8" along the western coast of Michigan's Mitten. There are high chance probabilities (>70%) for snowfall totals >4" along much of the northern tier communities of the Michigan U.P.. The WSSI shows Minor Impacts in these areas through Friday morning. ...Northern Rockies/High Plains... Days 1-3... Over the next few days, a series of upper level shortwave troughs will track from NW to SE across the region, providing both upper- level forcing and periodic rounds of Pacific moisture that foster periods of snow. The progressive nature of these disturbances and lack of deep moisture at mid-levels will help to keep most areas of heavy snow limited to the mountain ranges of central Montana, northern Wyoming, and the Black Hills. WPC probabilities show high chances (>70%) for >8" of snow in the Little Belt, Big Snowy, Absaroka, Big Horns, and Black Hills through Friday. The mountains that are most likely to see 1-2 feet of snow are the Little Belt, Big Snowy, and Big Horns, specifically in their taller/more remote peaks. ...Southeast... Day 1... ...Significant and historic winter storm concludes later this morning... The historic winter storm that produced heavy snowfall and disruptive ice accumulations along the Gulf Coast yesterday is producing heavy snow this morning in the Southeast from northern Florida to the southern Mid-Atlantic coast. Snow and ice should finally conclude around midday today, leaving frigid and near- record cold in its wake for the remainder of the week. WPC probabilities shows moderate-to-high chances (50-70%) for additional ice accumulations >0.01" in northern FL, especially west of the Jacksonville metro area. Additional snowfall accumulations of 1-2" are expected along the Southeast coast with the NC Outer Banks potentially receiving as much as 3" in some locations. In wake of this storm, travel will remain severely impacted tonight throughout much of the South with lingering icy conditions. See our Key Messages for more information that cover the final stages of this system, as well as the extreme cold over much of the eastern half of the Lower 48. Mullinax ...Winter Storm Key Messages are in effect. Please see current Key Messages below... https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_2.png