Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 417 PM EST Tue Nov 30 2021 Valid 00Z Wed Dec 01 2021 - 00Z Sat Dec 04 2021 ...Upper Midwest/Great Lakes to the Northeast... Days 1-3... A tranquil period with respect to winter weather is expected to continue, with no widespread heavy snowfall or significant icing expected across the contiguous United States over the next three days. Most of the accumulating snowfall through the period will be associated with a series of shortwaves embedded within progressive northwesterly to westerly flow across southern Canada. The leading system -- a wave lifting across Ontario into Quebec -- will support some warm advection precipitation across the Northeast into this evening, followed by a period of lake effect east of Ontario, as winds turn westerly overnight. This may produce some locally heavy accumulations in the Tug Hill region, where WPC probabilities are in the 40-70 percent range for accumulations of 4 inches or more in the Day 1 period -- ending 00Z Thu. Meanwhile, a wave moving across Alberta into Saskatchewan this afternoon -- is expected to push a warm front, with snow changing to rain across the Upper Midwest and northern Great Lakes tonight and Wednesday. An inch or two of snow is expected across the Minnesota Arrowhead and U.P. of Michigan. This will be quickly followed by a second wave sliding southeast across central Canada, nearing the northern Great Lakes Wednesday night. This system is forecast to track north of the Lakes, with little to no impactful snow expected over the U.S. Wednesday night into Thursday. Then as the system moves from Quebec into Atlantic Canada, westerly to northwesterly flow behind the system will support another period of lake effect snow showers off of the eastern Great Lakes, along with some upslope snows across the Adirondacks and northern New England Thursday night into early Friday. Probabilities for significant snowfall accumulations are low. For Days 1-3, the probability of significant icing is less than 10 percent. Pereira