Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 334 PM EST Sun Jan 30 2022 Valid 00Z Mon Jan 31 2022 - 00Z Thu Feb 03 2022 ...Pacific Northwest to the Northern Rockies... Days 1-2... An open wave off the AK Panhandle/BC coast this afternoon will continue to shift southeast, crossing WA this evening and the northern Rockies early Monday with a reinforcing trough axis following a similar path Monday/Monday evening. Ample moisture along the associated cold front will bring organized, moderate to locally heavy precipitation, including mountain snows, through the Cascade Mountains of Washington and northern Oregon this evening and the northern Rockies late tonight. Snow levels in the Cascades drop to around 2000ft through the main precip this evening with a risk for 8 or more inches at the Stevens and Snoqualmie passes. The frontal band will progress steadily east tonight, bringing locally heavy snows into portions of the northern Rockies, notably the Bitterroot Range in northern Idaho and the Rocky Mountain Front in northwestern Montana where snowfall over 8 inches is likely. Continued onshore flow, along with the reinforcing shortwave trough will support continued precip with snow levels around 1500ft for the Olympics, northern Cascades and the northern Rockies through Monday night. ...Central and Southern Rockies... Day 3... A pair of shortwave troughs shift east through the Northwest tonight and swing across the northern Plains late Monday before lifting north of the upper Great Lakes Tuesday with a strong reinforcing shortwave trough digging a long wave trough down the Intermountain West Tuesday night before swinging east over the southern Rockies Wednesday night. At the surface, a cold front will plunge south through the High Plains and Rockies Monday night. Post-frontal easterly flow, along with increasing synoptic scale ascent ahead of large scale trough amplifying over the West, is expected to support widespread mountain snows across the Colorado and northern New Mexico ranges Tuesday night/Wednesday. Locally heavy accumulations are most likely along the Sangre de Cristo Mountains and eastern San Juans, where Day 3 WPC probabilities indicate moderately high risk for accumulations over 8". ...South-Central Great Plains through the lower Great Lakes... ...Prolonged wintry mix event anticipated to begin over the south-central Plains and Midwest Tuesday night and shift south through Thursday... Day 3... A significant winter storm impacting portions of the central through interior northeastern U.S. begins Tuesday night over a swath from OK to the south tip of Lake Michigan as deepening moisture 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 southeast 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. As the trough digs over the Four Corners Wednesday, the forcing strengthens with only small southerly shifting in wintry precip given progression of cold air. Day 3 WPC snow probabilities are moderate for 6 or more inches from eastern KS through north-central MO/IL and northern IN while Day 3 ice probabilities are moderate for a tenth inch or more across southern MO/IL. The wintry threat area will shift south to Texas and the Mid-South Wednesday night as the upper trough ejects east over the southern Rockies. Jackson ~~~ 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 the middle of this week, bringing a variety of winter weather hazards including heavy snow, sleet, and freezing rain. -- For some areas, the storm will be prolonged with several rounds of winter weather lasting from late Tuesday through late Thursday. -- There is increasing confidence in significant snow accumulations from the southern Rockies through the eastern Great Lakes. A corridor of ice accumulation is possible from central Texas through the Ohio River Valley. -- Much below normal temperatures are also expected for mid to late week, especially across the Plains where temperatures 20 to 30 degrees below normal are likely. -- Plan now for travel disruptions and hazardous winter weather conditions.