Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 331 PM EST Sun Dec 03 2023 Valid 00Z Mon Dec 04 2023 - 00Z Thu Dec 07 2023 ...North-Central Rockies... Day 1... Moisture from the atmospheric river (AR) pushing into Oregon continues to be directed over the Intermountain West through WY and CO tonight. There are moderately high (40-80%) probs for an additional >6" snow for western WY and northern CO (into southern WY) ranges as snow levels rise from about 6000ft to about 7000ft. The next AR into the Pacific Northwest arrives late Monday night, but strong southwesterly flow directs this moisture into western Canada through Wednesday. ...Northern New York and New England... Day 1... A shortwave trough currently pushing northeast from OH this afternoon will cross New England tonight on the left side of a 150+kt SWly jet stream extending from the Mississippi Delta to New England. Continued development of a surface low currently over eastern Lake Erie that lifts to Lake Ontario is expected this evening when it is outpaced by the mid-level shortwave. Meanwhile, a coastal low on the right side of the jet streak will quickly shift northeast from the central Mid-Atlantic coast and past New England tonight. A surface wedge extending from a 1026mb surface high over northern Quebec will try to hold on in between as these two surface lows lift by. Into the overnight, strong ascent from left exit region of this powerful jet and low-to-mid level frontogenesis over this surface ridge axis will support the development of heavy precipitation with a wintry transition zone setting up over southern VT/NH and far southern Maine with snow banding to the north over the rest of northern New England including most of the Maine coast. Terrain enhancement can be expected over the Whites and Greens where 6-12" are forecast with Day 1 snow probs for >6" nearly reaching the coast in Down East Maine, continuing into Aroostook Co and over the northern Adirondacks. There are some lower (10-40%) probs for ice >0.1" in that transition zone over the highest Adirondacks, southern Greens, southwest NH, and interior southern Maine. Areas south of the CAD wedge axis, including Southern portions of NY and New England should expect rain with southerly flow until the low passes late tonight and precip near the coast cutting off thereafter. Northwesterly flow on the back side does allow upslope snow in the Adirondacks, northern Greens, and Whites into Monday night where an additional couple inches are likely. ...Central Appalachians... Days 2/3... An Alberta Clipper than shifts southeast across the Dakotas Monday amplifies as it crosses the Midwest Monday night and with the addition of Great Lake moisture Tuesday, forms a decent upslope snow case for the western slopes of the WV Appalachians above 2000ft to the Allegheny Front Tuesday afternoon and overnight into Wednesday. Thermally, this is an all snow case for the terrain here, but the saturation level struggles to get into the DGZ, so the overall potential is somewhat limited. Probabilities for >4" snow from 00Z Wed to 00Z Thur are 30-50% in the highest terrain west of the Allegheny Front. ...Western Washington... Day 3... Snow Levels rise to around 10,000ft Monday under a strong ridge and ahead and through the strong atmospheric river (AR) arrival. These high snow levels persist into Tuesday when height falls from an approaching trough direct the AR south back toward OR. Light to moderate precip continues over western WA Tuesday night/Wednesday as snow levels drop below 5000ft. Day 3 snow probs for >6" are currently low (10-30%) over the northern WA Cascades. Jackson