Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 340 AM EST Wed Jan 26 2022 Valid 12Z Wed Jan 26 2022 - 12Z Sat Jan 29 2022 ...Great Lakes/Northeast... Days 1-3... Broad cyclonic flow across the Great Lakes and eastern CONUS will be reinforced by a cold front Thursday, bringing impressive and renewed CAA across the Great Lakes. Despite the lack of any significant synoptic ascent through the period, pronounced NNW flow within the CAA each day will lead to favorable conditions for Lake Effect Snow (LES). First, a D1 cold front will bring a large area of light snow to the Upper Midwest eastward across the Great Lakes before LES picks up again as CAA increase post-FROPA. The most robust LES is likely south of Lake Michigan where a single convergent band is likely to develop with intense omega into a near-surface DGZ. WPC probabilities are low for 4+ inches at this time, but locally higher values are possible, and may be reflected better within the high-res guidance windows during later updates. ...Southern Appalachians through the Mid-Atlantic... Day 3... Shortwave energy dropping out of the Great Lakes Friday morning will attempt to phase with southern stream energy moving through the Southern Plains Friday afternoon. While guidance still features considerable spread in the timing and placement of these features, confidence is increasing that interaction will occur, in conjunction with an intensifying upper level jet streak (>150kts) arcing into New England and a 130kt subtropical jet across Florida. The overlap of these height falls, PVA, and strong/textbook upper diffluence is forecast to produce an area of low pressure off the SC/GA coast Friday and deepen rapidly as it lifts to the NNE. Over the Ohio Valley, height falls combined with increased moisture in the column will yield light snow into the southern and central Appalachians, aided by some upslope flow. There, WPC probabilities for at least 4 inches of snow is low to moderate but some higher locations could see close to six inches. To the east, organizing low pressure is forecast to deepen quite rapidly (perhaps 20mb in 12 h) by 12Z Sat as heights crash across the Carolinas, cold air is swept in from the NW and N, and any snowfall on the west side of the low is enhanced in convergent banding near and along the VA coast. To the north, rapidly occluding system will surge its warm conveyor belt northward into the Northeast with snow breaking out and increasing by Sat morning as warm advection punches northward. Several inches is likely along and east of I-95 from NJ northward to MA by 12Z Sat. The most intense snowfall is expected just beyond this period into New England. WPC probabilities for at least 4 inches of snow is moderate over southeastern VA and the DelMarVa late day 3. For days 1-3, the probability of significant icing is less than 10 percent. Fracasso/Weiss ~~~ Key Messages for Jan 28-30 East Coast Winter Storm ~~ - Confidence is increasing that a significant winter storm will create considerable impacts Friday through the weekend from the Mid-Atlantic through the Northeast. - Heavy snow is most likely in parts of New England, but is also possible farther south along the East Coast, including the major I-95 metro areas from New York City to Washington, D.C. - Significant coastal impacts are possible in the Northeast, including coastal flooding and beach erosion. Additionally, strong winds may cause blowing snow and some damage. - Hazardous travel conditions are likely in parts of the region. Please continue to monitor for updates, and check your local forecast at weather.gov