Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 355 AM EST Fri Feb 07 2020 Valid 12Z Fri Feb 07 2020 - 12Z Mon Feb 10 2020 ...Northeast... Day 1... A rapidly intensifying low will track from the Mid-Atlantic this morning and pass eastern Maine this evening on a powerful southerly jet. Rapid post-frontal cooling is expected in the deformation axis to the left of the track with a rapid changeover from rain to heavy and impactful snow in this tight zone across PA/NY through midday then across far northern New England this afternoon/evening. Snowfall rates of 1 to 2" per hour are likely on the immediate cold side of the transition zone. Day 1 snow probabilities are high for six or more inches (much of this falling in six hour or less) in a swath from north-central PA across Upstate NY generally east of Lake Ontario and west of the Hudson River. Low-mid level warm advection persists into the afternoon across eastern/central New England, spreading the ongoing freezing rain over Upstate NY to the southern Adirondacks, Green Mtns of VT, the Monadnocks of NH...and southern/eastern Maine where probabilities are moderate for an additional tenth inch for Day 1. The departure of the low tonight across the Canadian Maritimes ends the synoptic portion of the event, with precip in Maine quickly winding down this evening. ...Northwest... Day 1 into Day 2... Confluent flow arcing from the Pacific Northwest down the northern Rockies to CO slowly weakens today as jet dynamics decrease ahead of the next trough that reaches Vancouver Island this evening. Snow rates decrease today with moderate to high probabilities for an additional 8 or more inches for the Olympics/WA and northern OR Cascades, the Blue Mountains of OR and the northern Rockies of ID/MT/WY, the northern Wasatch of UT and the northern CO Rockies. Snow levels drop with the trough crossing WA tonight with northern stream energy shearing off and tracking east to the northern Great Plains Saturday as the main trough takes an interior track down the West Coast through Sunday. The eastward track of the northern stream energy gives enough lift for Day 2 snow probabilities for 8 or more inches for the WA/OR Cascades, Blue Mountains, northern ID/western/central MT and northern WY mountains. ... Northern Great Plains across Upper MS Valley to The Great Lakes... Days 2/3... Northern stream shortwave energy ejects east from the northern Rockies Saturday, crossing SD as a clipper Saturday night, southern MN/WI Sunday and the central Great Lakes Sunday night. A low-mid level frontogenesis max develops north of this 850 mb low track which taps Gulf moisture and allows narrow banded snow to develop. A mesoscale band of 6-10 inches is likely in these areas with much of the precip type expected to be rain. The uncertainties involve precip type with a change over to mixed types and rain along and south of the 850 mb low track, along with a tight QPF gradient north of the frontogenesis zone. Good agreement among global guidance Saturday night and Sunday warrants moderate Day 2.5 probabilities for 6 or more inches from eastern SD across southern MN and through WI per the Day 3 snow probabilities. The probability of freezing rain greater than 0.25 inches is less than 10 percent Days 2-3. Jackson