Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 333 AM EST Fri Feb 26 2021 Valid 12Z Fri Feb 26 2021 - 12Z Mon Mar 01 2021 ...Pacific Northwest to the Northern Rockies... Days 1-2... Strong northwesterly flow, with one last shortwave moving across the area today, will continue to support periods of heavy snow across the Northwest into the northern Rockies through early Saturday. Through D2, widespread additional accumulations of 8-12 inches are likely across the Olympics, the Washington and Oregon Cascades, the Blue Mountains, as well as the Rockies from northern Idaho and western Montana to eastern Idaho and western Wyoming. Within these areas, local accumulations of 2-feet or more are likely across the higher elevations of the Cascades, the Blue Mountains and the Bitterroot Range. Drier weather is expected by late Saturday and continuing into Sunday as a strong ridge shifts east across the region. ...Upper Midwest... Day 3... A shortwave embedded within a positively tilted trough will skirt northeast from the Central Plains Saturday night into Sunday before racing off into Canada Sunday evening. This feature will be accompanied by a modest but strengthening upper level jet streak which will amplify and turn poleward leaving favorably LFQ diffluence atop the region. The combination of these features will create a fast moving but deepening surface low pressure which is progged to lift from Iowa Saturday night into Ontario Sunday evening. While the guidance has again trended stronger with this wave, it is still likely to be a modest and fast moving event. WPC probabilities are indicative of this as well, with only a narrow corridor of 4" probabilities greater than 10%, focused in far northern WI and into the U.P. of MI. In this area, there exists the best overlap of fgen and omega within the DGZ, suggesting a potential band of heavier snow on the NW side of the low. While this is not likely to be too robust, it should be enough to create some enhanced accumulation Sunday morning. ...New England... Day 2... Broad cyclonic flow across the east will produce SW flow into New England, within which a weak shortwave impulse will lift out of the Mid-Atlantic late Saturday, with a subsequent impulse passing by just to the north across southern Canada Sunday. Moist SW flow aloft will help spread precipitation northward ahead of a warm front, with increasing jet level diffluence for ascent aiding to expand the precip coverage. While WAA will change much of New England over to rain after an initial period of snow, as a wave of low pressure develops off New England and shifts east, just enough ageostrophic flow from the north combined with the higher elevations (and colder temperatures) across Northern New England should lead to a period of moderate to heavy snowfall Saturday into Sunday. The guidance has trended a bit wetter with this system as well, and this has led to an increase in WPC probabilities for 4 inches, which are now high in portions of NH and ME, generally above 3000 ft. For Days 1-3, the probability of significant icing (0.25-inch or greater) is less than 10 percent. Weiss