Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 435 PM EST Fri Feb 05 2021 Valid 00Z Sat Feb 06 2021 - 00Z Tue Feb 09 2021 ...Great Lakes... Day 1... Ongoing lake effect event is expected to continue across the Upper Great Lakes, with deep cyclonic flow supporting additional locally heavy accumulations along the Keweenaw Peninsula and along the west to northwest snow belts in the eastern U.P. of Michigan. Lighter accumulations are expected along the eastern shore of Lake Michigan. Southwesterly to westerly flow and strong cold air advection will support single band development across Lake Erie and Lake Ontario, with locally heavy accumulations expected beginning this evening and continuing into Saturday across the Buffalo and Tug Hill regions of New York. ...Pacific Northwest to the Northern and Central Rockies and High Plains... Day 1-3... Periods of light to moderate snow are expected to continue into the overnight across the northern and central Rockies as mid level energy embedded within strong northwesterly flow, interacts with a sharp boundary draped across the region. As the leading shortwaves move into the Plains on Saturday, guidance shows another well-defined shortwave dropping southeast into the Pacific Northwest -- supporting the development of additional organized heavy snows from the northern Cascades into the northern Rockies, with lighter snows spreading east into the northern High Plains. Periods of snow are expected to continue through Monday, however lighter accumulations are expected. Three day totals of 2-feet or more are likely for portions of the northern Cascades, as well as the northern Idaho and western Montana ranges. Totals of 1-foot or more are likely across the central Montana to the northwestern Wyoming ranges. ...Central Plains to the Mid Mississippi Valley... Days 1-3... As energy emanating from the West moves through the base of the broader scale trough -- this favorable forcing aloft along with strong low-to-mid level frontogenesis will support banded snow moving progressively southeast across Nebraska into northeastern Kansas, northern Missouri and southern Iowa Friday night and Saturday. Strong forcing along with high snow-to-liquid ratios have helped to bolster the potential for locally heavy totals, with probabilities for accumulations of 4-inches or more increasing across portions of Nebraska. As the previously noted upstream energy in the Northwest makes its way into the region, a second round is expected to develop Saturday night and continue into Sunday with some potential for locally heavy accumulations as well. ...Southern Appalachians to the Mid-Atlantic and Northeast... Days 1-2... Models continued to offer an increasing signal for significant snows developing over the southern Appalachians and spreading east, as a well-defined shortwave moving through the base of the broader scale trough swings across the Tennessee valley into the southern Appalachians Saturday night. Coastal low developing near the North Carolina coast Sunday morning is forecast to track northeast, close enough to the coast to support the potential for significant snows spreading northeastward from southwestern Virginia to the Delmarva and New Jersey, and then across southern New York and New England Sunday morning. This includes the Richmond/DC to the Boston metro regions. While confidence in the details has been limited by the run-to-run changes over the past several models runs, there are increasing probabilities for snow accumulations of 4-inches or more across these areas, with locally heavier totals becoming more likely. For Days 1-3, the probability of significant icing (0.25-inch or greater) is less than 10 percent. Pereira