Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 413 PM EST Thu Feb 27 2020 Valid 00Z Fri Feb 28 2020 - 00Z Mon Mar 02 2020 Days 1-3... ...Great Lakes... A strong low pressure system currently lifting north into the St Lawrence valley is expected to slow and gradually weaken over southern Quebec on Friday. Strong, westerly winds to its south will continue to support heavy lake effect snows east of lakes Erie and Ontario through Friday, with multiple feet likely in some locations. Heaviest amounts are expected to fall east of Lake Ontario into the Tug Hill region, where powerful westerly winds are expected to focus an intense narrow band with an upstream connection to the Upper Lakes. Snows are expected to shift south Friday night as winds before more northwesterly before diminishing by late Saturday as high pressure and drier air builds across the region. WPC PWPF indicates additional amounts of a foot or more are likely east of both lakes - in the Tug Hill region and western New York, with two feet or more likely in the Tug Hill. Meanwhile, northwesterly winds will support locally heavy snows across portions of the eastern Upper Peninsula and northern Lower Michigan through the overnight into Friday. WPC PWPF shows high probabilities for additional amounts of 4-inches or more portions of these areas. ...Central and Southern Appalachians/Cumberland Plateau... Deep cyclonic, westerly flow with embedded mid-level energy will continue to support snow showers through Friday, with impactful accumulations possible along the upslope regions. Models are showing a pair of better defined shortwaves diving southeast through the central Plains and moving through the base of the broader scale trough. These features may support periods of more organized precipitation Friday into early Saturday, raising the potential for locally heavy accumulations across the region. WPC PWPF indicates that additional accumulations of 4-inches or more are likely for portions of the Allegheny mountains in West Virginia and along the southern Blue Ridge. ...Western U.S.... Mountain snows are expected to return to the Pacific Northwest and the northern Rockies as a well-defined trough drops into the region Friday night. As the system moves across the region Friday night and Saturday, WPC PWPF indicates that local amounts of a foot or more are likely for the higher elevations of the Olympics and northern Cascades. This system is expected to continue to amplify and dig southeast, with models indicating an elongated positively-tilted trough dropping southeast across the western U.S. on Sunday. This will support widespread mountain snows, with locally heavy totals from the Sierra to the northern Rockies. WPC PWPF shows high probabilities for snowfall accumulations of a foot or more for portions of the western Wyoming and northern Utah ranges, where strong low level forcing coinciding with a boundary dropping south across the region is expected to support heavier totals Saturday night and Sunday. For Days 1-3, the probability of significant icing (0.25-inch or greater) is less than 10 percent. Pereira