Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 342 PM EST Sat Dec 05 2020 Valid 00Z Sun Dec 06 2020 - 00Z Wed Dec 09 2020 ...New England... Day 1... ...Significant Nor'easter continues into Sunday... A well developed, phased low currently approaching Cape Cod from the south will lift north across the Gulf of Maine tonight and slow to a northerly drift over New Brunswick Sunday and the Gulf of St. Lawrence Sunday night as it weakens/fills. A rain/snow line that setup under the TROWAL today over southeast New England (central Mass down across east-central CT) has shifted southeast into eastern Mass and RI (per KBOX correlation coefficient) and will continue to drift southeast across the Boston metro to Cape Cod this evening as the low center crosses Cape Cod and continues north into the Gulf of Maine. This rain/snow line sets up as a coastal front north of Boston along the NH/and southern ME coast per KGYX. Moderate to heavy snow with rates of 1+"/hr will continue on the cold side of the line for several more hours. Marginal surface temperatures are overcome by the heavy rates from idea dendritic snow growth aloft and nocturnal trends and cold air advection/reinforcing of the coastal front will allow for more efficient snowfall tonight. WPC probabilities are underdone for the NH/ME coast due to too strict surface temperature requirements for accumulating snow (air temperature <1C) and global models underdoing dynamic cooling from the heavy band. Day 1 snow probs are moderate to high for 8 or more inches well inland over northern NH and interior ME, though this can be extended to the coastal front. The occluded low loses its direct connection to Gulf Stream-sourced moisture Sunday with precipitation rates decreasing on the west then southwest side of the low as it lifts through the Canadian Maritimes with the risk of heavy snow shifting north from Maine Sunday. For Days 1-3, the probability of significant icing (0.25-inches or greater) is less than 10 percent. Jackson