Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 428 PM EDT Wed Mar 23 2022 Valid 00Z Thu Mar 24 2022 - 00Z Sun Mar 27 2022 ...Upper Midwest/Great Lakes... Days 1-3... A wintry mix associated with a broad area of low pressure lifting northeast across the Midwest/Great Lakes is expected to produce some additional snow and ice accumulations through this evening across portions of the northern Great Lakes region. For most areas, accumulations are expected to be light. For the evening into the overnight period, guidance does show an area of strong upper divergence associated with left-exit region upper jet forcing centered over northern Lower Michigan and the eastern U.P. This may raise the potential for heavier precipitation rates and is reflected in localized higher WPC probabilities for additional ice accumulations of 0.10 inch or more and 1-2 inches of snow across the region during the evening to overnight hours. On Friday, a well-defined clipper system is forecast to dive southeast across the Upper Midwest. This is expected to bring some synoptic, mainly light snows from eastern North Dakota across northern Minnesota on Friday. Lake effect snows downstream of the upper lakes are expected to develop by late Friday and continue into the weekend. A prolonged period of northwesterly flow could support some locally heavy amounts in the U.P. and northern Lower Michigan. ...Northeast... Days 1-2... Warm advection precipitation associated with the low over the Midwest will continue to spread north across the Northeast this evening, through the overnight, and into tomorrow. As warm air aloft spreads across the region, models continue to show a shallow cold air wedge developing at the surface. This will support a wintry mix, with accumulating ice likely across the higher elevations of northeastern Pennsylvania, eastern Upstate New York, into central and northern New England tonight into tomorrow. For the Catskills, Adirondacks, Berkshires, and Greens -- WPC probabilities indicate that ice accumulations of 0.10 inch or more are likely across portions of those areas. As a well-defined shortwave moving through the base of the broader scale trough lifts into the Northeast, a low is expected to develop and track along the Northeast coast Thursday night into Friday morning -- bringing the potential for significant wintry precipitation across northern Maine. In the WPC guidance, high probabilities for snow accumulations of 4 inches or more are indicated across northern Aroostook County. ...Central Appalachians... Day 3... The clipper system sliding across the Upper Midwest on Friday is expected to continue across the Ohio Valley and central Appalachians on Saturday. This is forecast to be a very dynamic system, with models indicating a closed 500 mb center dropping southeast from the Great Lakes into the Ohio Valley Friday night. Strong forcing aloft along with upslope flow may support a period of at least moderate snow across the higher elevations of the southern Allegheny mountains early Saturday. In the wake of the system, deep northwesterly flow and strong cold air advection will likely support lake effect and orographic snows from the Lower Great Lakes into the central and southern Appalachians. Heaviest snow accumulations are excepted to focus along the southern Allegheny Mountains, where WPC probabilities indicate that 2-4 inches are likely, with heavier amounts possible across the higher terrain. Pereira