Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 341 AM EDT Fri Oct 30 2020 Valid 12Z Fri Oct 30 2020 - 12Z Mon Nov 02 2020 ...Northeast... Days 1-2... A mid-level wave crossing southern New York/southern New England combines with mid level frontogenesis to produce continued light precipitation across these areas early today. Low level cold advection is starting to turn rain over to snow in interior New York/New England and the rain to snow transition zone should move south today. Model liquid equivalent precipitation amounts hover near 0.25 inches. This split into both rain and snow means most locations should receive modest accumulations with 1-3 inches common in higher elevations, with little along the southern New England coast. The event ends as the mid level wave and ascent departs this evening and drying aloft commences. ...Pacific Northwest... Day 1... A 700 mb shortwave moving west to east across WA State today will be accompanied by a Pacific jet streak and surface cold front to produce snowfall in the high terrain of the WA Cascades and Northern Rockies. Snow levels will generally be high, so significant accumulating snow should be confined to the highest terrain. Snow levels will fall with the passage of the shortwave and cold front, but drying aloft will bring an end to the precipitation as the wave moves east of the region. ...Great Lakes... Days 2/3... A strong cold front moves across the Lakes Saturday night into Sunday. Behind this front, strong cold advection across the still warm lake waters will produce a favorable for lake effect snow as N/NW winds develop across Lake Superior and then Michigan. Accumulations are favored St night int he western UP of Michigan/Keweenaw peninsula, close to a mid level deformation zones as the 700 mb wave progresses through the region. On Sunday, as the wave moves slowly east, the deformation band shifts east into the eastern UP of Michigan, so snow showers should focus there. Drying aloft develops in the western UP to limit snowfall duration and thus amounts on Sunday. On the flip side, the mid level wave and moisture feed crossing norther lower MI favors a period where moist flow turns upslope in the windward terrain north northwest lower MI, so snow showers are likely there Sun with several inches possible. Drying develops here Sunday night and low level convergence weakens, so snowfall in northwest lower MI should taper Sun night. The probability for significant ice (0.25" or greater) is less than 10 percent all 3 days. Petersen