Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 334 PM EST Sun Jan 26 2020 Valid 00Z Mon Jan 27 2020 - 00Z Thu Jan 30 2020 ...Northwestern CONUS... Days 1-3... In a series of progressive shortwaves to impact the Pacific Northwest, snowfall accumulations are expected to primarily affect higher elevations of northern CA, western OR, and western WA with the highest probabilities of heavier snow totals across the WA Cascades due to relatively high snow levels elsewhere. The highest amounts through tonight are forecast to be in the WA Cascades due to the longer duration of overlapping lift/moisture. Another surge of moisture and lift associated with the upper level jet maxima and low level warm advection is expected to produce another round of locally heavy snow in the northern OR Cascades and WA Cascades Monday into Monday night. A break looks to develop on Day 3 in the WA Cascades as the upper trough moves onshore and inland, with drying aloft developing in its wake. Across portions of central/northern ID and northwest MT, several inches are snow are expected as the repeating shortwaves track through the central/northern Rockies. While no particular system is likely to produce widespread heavy snowfall, the cumulative affect over the next 3 days will produce considerable accumulations for the highest elevations. The combined moisture transport and lift extends inland into the Blue Mountains of northeast OR. The 3 day totals show the potential for a foot or more across the ranges of northeast OR to southern ID and northwest WY. Lighter snowfall totals will spread southeast across areas with upslope flow in the Great Basin and CO/NM. Snow should taper Tuesday morning as the upper trough departs and moves east onto the Plains. ...Lower Great Lakes/New York/northern New England... Days 1-3... Strong cyclonic flow in the wake of the departing system will bring a prolonged period of enhanced moisture and lift across both Lake Erie and Lake Ontario. Aided by the favorable west/southwest flow and enhancement due to topography, several inches of snow are expected in the lee of both lakes across southwest and upstate New York. On Monday, amounts are lighter as a progressive front crosses the lower lakes, with lighter snow amounts following shorter cross lake trajectories and weaker lift. Most locations on Monday are forecast to get an inch or two, with no heavy snow areas identified. ...Southern Plains... Day 3... A compact shortwave trough and associated area of low pressure drops out of the central Rockies toward the southern/south-central Plains Monday into Tuesday. As the wave digs into the OK/TX Panhandles, colder air surges on the backside of the system and a changeover from rain to snow is expected. Despite the progressive nature of the system, sufficient amounts of moisture and lift could produce several inches of snow in a localized area. The forecast was blended toward the solutions from the ECMWF, NAM, and some members of the hi-res guidance. As the system progresses eastward toward the lower MS Valley, probabilities of frozen or mixed precipitation decrease due to relatively warmer boundary layer temperatures. The probability of 0.25 inches of freezing rain is less than 10 percent Days 1-3. Taylor