Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 336 AM EST Tue Feb 25 2020 Valid 12Z Tue Feb 25 2020 - 12Z Fri Feb 28 2020 ...Mid Mississippi Valley to the Upper Great Lakes... Days 1-2... An 850 mb front with an embedded elongated circulation drifts slow east northeast today across the mid Mississippi valley into the Oh Valley, continuing downstream across the Great Lakes Wednesday. A band of moderate to heavy snow is expected to develop in the low-to-mid level frontogenesis and deformation zone on Wed. The night time model runs showed a continued trend toward a more southeast axis of snow, but not as much as a shift as last night. The latest model consensus now shows light to moderate amounts from northeastern Missouri and central IL and northwest IN. The amounts increase in northeast IN, northwest OH and southeast lower MI on Day 2 as the sfc-700 mb low starts to strengthen. The models are still showing the potential for some lake enhanced, heavier amounts along the shores of Lake Huron to western Lake Erie. The event unwinds as low pressure sfc-aloft moves across the border into Canada. There is potential for 6-8 inches of snow in southeast lower MI and adjacent northwest OH. Northeast/Lower Great Lakes... Days 2/3... As the upper trough crosses the Great Lakes, an upper jet maxima is forecast to move along the spine of the Appalachians, with a well-defined 300 mb divergence maxima crossing PA/NY into interior New England Wed night night to Thursday morning. This will combine with low-mid level warm advection to produce widespread precip across New York into New England Wed night and Thursday. Expect Wed/Wed night warm advection will likely limit snowfall potential at lower elevations, including the major cities. The combination of synoptic lift and upslope flow into the NY Adirondacks, the VT Green Mountains, and NH White Mountains to the ranges of interior Maine will support the potential for several inches of snow Wed night, continuing on Thu across interior Maine until the upper divergence maxima crosses into Canada later Thu. There is potential for foot of snow across interior Maine Wed night through Thu. Once the upper trough arrives Thu, cold advection develops across Ontario and Lake Ontario. West boundary layer winds down the major axis of the lake enhanced moisture and heat fluxes from Lake Ontario, leading to heavy snow developing in the Tug Hill to the western Adirondacks. The prolonged westerly flow with a long cross -lake trajectory leads to confidence in a heavy snow event, with potential for a foot of snow on the east end of Lake Ontario into the Tug Hill. For Days 1-3, the probability of significant icing (0.25-inch or greater) is less than 10 percent. Petersen