Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 347 AM EST Tue Feb 01 2022 Valid 12Z Tue Feb 01 2022 - 12Z Fri Feb 04 2022 ...Central and Southern Rockies... Days 1-2... Shortwave moving through the northern Plains overnight will lift to the northeast into Ontario as a trailing cold front plunges southward through the northern Plains and Rockies. Post-frontal easterly flow, along with increasing synoptic scale ascent ahead of an amplifying trough digging through Utah and Arizona, is expected to support widespread mountain snows across the Colorado and northern New Mexico ranges by late today, with locally heavy accumulations possible by early Wednesday and modest accumulations across the Front Range. Higher WPC probabilities for at least 4 inches of snow are mainly west of the Colorado I-25 corridor, although some higher probabilities center near the Wyoming-Colorado border into the Cheyenne metro on Day 1. The potential for heavy snow is expected to increase across southern Colorado and northern New Mexico and spread south on Wednesday. Upper trough will move east out of Arizona into/through New Mexico, enhancing northeasterly flow and the development of heavy snows spreading south through the central/southern New Mexico ranges (as well as over parts of eastern Arizona) Wednesday night into Thursday morning before tapering off later Thursday. The San Juan and Sangre de Cristo mountains are expected to see some of the highest two day totals, with WPC probabilities indicating amounts of a foot or more are likely with the highest totals between 2-3 feet. ...South-Central Great Plains through to the Northeast... ...Several rounds of winter weather lasting through Thursday for portions of the central U.S. before shifting to the interior Northeast... Days 1-3... Tuesday night into Wednesday morning is expected to mark the onset of what will likely become a prolonged, multi-round and multi-precipitation type winter weather event impacting a large portion of the central to northeastern U.S. into Friday. Deepening moisture (precipitable water anomalies of +1 to +3 sigma near and south of the front) supplied by low-to-mid level southerly flow from the Gulf of Mexico into the central U.S. is expected to support precipitation developing north of a strong cold front as it drops southeastward through the central Plains, mid-Mississippi Valley, and south of the western Great Lakes Wednesday morning. Favorable upper jet forcing overlapping mid-level frontogenesis is expected to support an expanding area of wintry precipitation from Kansas and Oklahoma to Lower Michigan Day 2. Precipitation will continue to develop and propagate northeastward in tandem with an increasing jet (~150kts) into the Corn Belt as another area of organized precipitation develops back to the southwest. As the upper trough in the Southwest moves into the southern Plains, right-entrance region upper jet forcing along with the strong low-to-mid level frontogenesis will support an area of moderate to heavy snow developing over eastern Oklahoma and Kansas Wednesday evening before shifting northeast through the mid-Mississippi Valley and into the southern Great Lakes region overnight. On Thursday, strong divergence along the right-entrance region of a powerful upper jet (~170kts centered over the northern Great Lakes), will continue to combine with low-to-mid level frontogenesis to support moderate to heavy snow continuing northeast through the eastern Great Lakes into the Upstate New York and northern New England. WPC probabilities indicate that total snows of at least 4 inches are likely to extend from Kansas and portions of Oklahoma all the way to northern Ohio and southern Michigan. Within this area, locally heavier totals reaching a foot or more are most likely from central Illinois through northern Indiana into Lower Michigan. By early Friday, snowfall amounts of 8 inches or more are likely from western New York to the Adirondacks and along the northern New England border. Heavier totals of up to a foot or more are most likely across western New New York and the Adirondacks. South of the heavier snow, a wintry mix, including freezing rain, will likely impact areas from North Texas into the Ohio Valley Wednesday into early Thursday, extending farther northeast through the central Appalachians into the Northeast. Significant ice accumulations are likely, with amounts of a 0.25 inch or more possible, especially across portions of eastern Oklahoma, northern Arkansas, southern Missouri/Illinois and northeastward along and north of the main stem of the Ohio River. There, WPC probabilities of at least 0.25 inch ice are in the moderate (40-70%) category. Pereira/Fracasso ~~~ Key Messages for Feb 1-3 Winter Storm ~~ -- A large and significant winter storm is expected to impact much of the central U.S. beginning tonight, bringing a variety of winter weather hazards including heavy snow, sleet, and freezing rain. -- The storm will be prolonged with several rounds of winter weather lasting through Thursday for portions of the central U.S. before shifting to the interior Northeast. -- Heavy snow is expected over the southern Rockies and from the south-central Great Plains through the eastern Great Lakes and interior Northeast. A corridor of heavy ice accumulation is likely from Texas through the Ohio River Valley. -- Locations impacted by snow and/or ice are expected to have temperatures remain below freezing, and well below average, for at least a couple days after the wintry precip ends. -- Plan now for prolonged hazardous winter weather conditions and disrupted travel.