Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 358 PM EST Sat Mar 12 2022 Valid 00Z Sun Mar 13 2022 - 00Z Wed Mar 16 2022 ...Northeast.. Day 1... A strong low pressure system will continue to deepen as it lifts away from New England and into the Canadian Maritimes. A residual deformation band will pivot across northern Maine tonight before ending from SW to NE by Sunday morning. As this low pulls away, drier air will advect in from the west bringing an end to most of the snowfall. However, intense NW flow and CAA beneath a deep longwave trough will produce, upslope snow into the terrain of upstate NY and Northern New England, light LES off Lake Ontario, and modest snow showers within the instability pool through early Sunday. Most of this snowfall should be light, but WPC probabilities for at least 4 inches of snow are 10-30% across northern Maine, the White Mountains of NH, and the Northeast Kingdom of VT. ...Upper Midwest... Day 2... A potent jet streak racing west to east across the Northern Plains and Upper Midwest will drive ascent atop an elevated baroclinic gradient north of a cold front sinking into the Mid-MS VLY. A weak wave of low pressure along this front will shift southeast, driving subtly enhanced warm advection which will isentropically ascend the Canadian high to produce an expanding precipitation shield from North Dakota through the western Great Lakes. The most robust overlap of forcing and moisture is likely from eastern MN through the U.P. and northern L.P. of MI, where some enhanced fgen is likely to drive heavier snow rates. This feature will move quickly eastward, but WPC probabilities for more than 4 inches are as high as 10% in a narrow corridor from WI through MI. ...Pacific Northwest... Days 1-3... Two distinct shortwaves will move onshore Washington State during the next three days, each one accompanied by Pacific jet energy and a surface cold front. The combination of the upper jet and WAA ahead of the surface front will increase moisture into the region, upon which the deep layer ascent will produce snowfall in the terrain of the region. Each shortwave is potent and compact, but also fast moving as the mid-level flow remains pinched. Shortwave ridging between the two features will reduce snowfall on D2, but heavy snow is likely both D1 and D3. For D1, WPC probabilities are high for 6+ inches in the OR Cascades, with moderate probabilities extending into the Blue Mountains, the Sawtooth, parts of the Northern Rockies, the Tetons, and the Wind Rivers. The second impulse will be displaced a but further north than the lead shortwave, and WPC probabilities for more than 6 inches are high in the WA Cascades and Olympics, with moderate probabilities extending into the Northern Rockies. Weiss ~~~ Key Messages for the Tennessee Valley through Northeast Winter Storm ~~~ - Periods of heavy snow will continue across Northern New England through early Sunday bringing an additional 3-6 inches of snowfall. This snow will combine with gusty winds to produce hazardous travel and isolated power outages. - Elsewhere across the Northeast, brief heavy snow showers and isolated snow squalls may produce reduced visibility and hazardous travel. - Behind the storm, record cold is likely for much of the Southeast tonight as temperatures fall below freezing as far south as the Gulf Coast and northern Florida. - With rapidly falling temperatures tonight, untreated surfaces that remain wet will re-freeze, leading to slippery roadways and sidewalks.