Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 324 PM EST Fri Jan 28 2022 Valid 00Z Sat Jan 29 2022 - 00Z Tue Feb 01 2022 ...Southern Appalachians through the Mid-Atlantic... Days 1-2... ...Powerful Nor'easter/Blizzard for the Mid-Atlantic and Northeast... A powerful low pressure system will rapidly develop tonight just off the Mid-Atlantic coast tonight as the associated upper trough assumes a negative tilt before closing Saturday. The surface low bombs out with the central pressure dropping more than 24mb between 00Z tonight and 00Z Sunday, an indication of the powerful winds that will be associated with the system. Strong upward ascent supported by a coupled upper jet and low-to-mid level frontogenesis will promote the development of moderate to heavy snow on the northwest side of the low. 12Z HREF guidance indicates mean ensemble hourly snowfall of 1" developing along the Delmarva coast late this evening, the Jersey Shore and Long Island overnight, and across southeastern New England through the day Saturday, and across eastern Maine Saturday afternoon into the evening. The highest mean hourly snowfall is 2 to 2.5" over southeastern Mass Saturday late morning through the middle afternoon and along coastal Maine and Down East Main Saturday afternoon. For the 48-hour period ending 00Z Monday, WPC probabilities indicate an 80% chance for exceeding 18" between Boston and Cape Cod with 40% values stretching from the central Jersey Shore to central Long Island and through interior eastern New England. Probabilities for over 8" of at least 40% stretch from the Delmarva through the Northeastern Urban Corridor and pretty much all of Maine. There is a risk for over 30 inches, particularly in southeast Massachusetts where repeating bands of ocean enhanced snow will maximize accumulations in spite of dendritic fracturing due to 50 to 70kt flow in the DGZ. Meanwhile, upper level forcing will allow a large comma head precipitation shield to support snow showers moving southeast across the southern Appalachians to the Carolina Piedmont. There are moderately high probabilities for 4 inches in the Smokies, and 20 to 40 percent probabilities over west-central NC into north-central SC, including Charlotte. ...Pacific Northwest to the Northern Rockies... Days 2/3... An upper low moving across the Gulf of Alaska on Saturday is expected to transition to an open wave, with energy shearing southeast across western Canada and the Pacific Northwest and the northern Rockies Sunday night into early Monday. This will bring a frontal boundary and increasing moisture into the region, supporting the return of precipitation, including the potential for heavy snows across portions of the northern Cascades and Bitterroots with snow levels generally 3500ft. For days 1-3, the probability of significant icing is less than 10 percent. Jackson ~~~ Key Messages for Jan 28-30 Blizzard ~~ -- A major winter storm will bring widespread impacts to the I-95 corridor from the Mid-Atlantic to New England. Snowfall accumulations greater than 12†are expected along portions of the Mid-Atlantic coast through eastern New England with local maxima greater than 24†across eastern Massachusetts including the Boston metro. -- Heavy snow rates and strong winds will produce dangerous blizzard conditions along portions of the Mid-Atlantic and New England coasts. Expect whiteout conditions and nearly impossible travel at times. The strong to damaging winds will lead to scattered power outages. -- Significant coastal impacts are possible, including coastal flooding and beach erosion. -- Very cold temperatures will follow the storm with dangerous wind chills Saturday night into Sunday morning.