Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 236 AM EDT Wed Mar 26 2025 Valid 12Z Wed Mar 26 2025 - 12Z Sat Mar 29 2025 ...Northeast... Day 1... Compact upper low over southwestern Ontario this morning will move across northern NY/VT midday and through Maine this evening. This will spur some more light snow into the Tug Hill Plateau where 1-3" is likely. Farther east, low probabilities (10-30%) are shown for more than 4 inches of snow over the Green and White mountains via upslope enhancement as the feature moves through. ...Upper Midwest/Great Lakes/Northeast... Days 2-3... Flattening upper ridging exiting the High Plains Thursday combined with lee-side surface cyclogenesis centered over South Dakota Thursday night will favor broad WAA-driven precipitation along and north of a surface boundary astride the Upper Midwest into the Great Lakes. With the fast zonal/progressive flow, this will quickly expand eastward through Canada and into the Northeast with an influx of moisture from the southwest, reaching into NY Fri evening then into New England overnight into early Saturday. Temperatures are marginal for most areas, confining wintry precipitation to areas closer to the Canadian border. However, that sub-freezing surface layer will be overrun from the S/SW with warmer air aloft, promoting a rather large area of sleet/freezing rain from northern MN eastward across the U.P. of Michigan and northern WI across Ontario and into the Adirondacks. Ptype from the models (and NBM) show a strong signal for freezing rain (impressive for late March), but this may be modulated my afternoon insolation. Nevertheless, WPC probabilities for at least 0.10" icing are moderate (30-70%) over northeastern MN, the U.P./northern WI, and the northern part of Lower Michigan. Snow amounts may be limited, with the highest amounts of a couple inches over northern MN where WPC probabilities for at least 4 inches are barely 10%. ...Cascades into the northern Sierra Nevada... Days 2-3... An anomalously deep, cold core low in the northeast Pacific will curl up toward Vancouver Island as its wound up occlude front moves inland tonight. High snow levels (>8000ft) this afternoon will steadily drop to around 4000-5000ft tomorrow, then to around 4000ft Friday with the passage of the upper trough. Snow will eventually get to some of the passes but much of this will fall over the higher terrain. Two-day probabilities of at least 8 inches of snow are highest above 5000ft or so along the Cascades southward to the NorCal ranges and northern Sierra. Moisture will continue inland to the northern Rockies with a few to several inches of snow for the Blue Mountains and into SW MT as a frontal boundary in the area acts as another focus for forcing. There, WPC probabilities for at least 8 inches of snow are low (10-30%). Fracasso