Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 417 AM EST Mon Jan 31 2022 Valid 12Z Mon Jan 31 2022 - 12Z Thu Feb 03 2022 ...Pacific Northwest to the Northern Rockies... Days 1-2... A leading shortwave trough will continue to move east of the Cascades and across the northern Rockies later this morning. In its wake, northwesterly flow with embedded shortwave energy will support the continuation of unsettled weather through Tuesday. This includes a well-defined shortwave associated with a remnant upper low that is forecast to drop into the Northwest later today. WPC probabilities indicate that additional accumulations of 8-12 inches, with locally heavier amounts, can be expected through early Wednesday across portions the northern Cascades, as well as the Blue Mountains, and parts of the northern Rockies. This includes portions of the Bitterroots in northern Idaho and the Glacier region in northwestern Montana. With snow levels remaining low, additional significant accumulations are expected within the northern Cascade passes. ...Central and Southern Rockies... Days 2-3... The leading shortwave moving into the Northwest on Sunday is expected to swing across the northern Plains late Monday-early Tuesday before lifting north of the upper Great Lakes Tuesday evening. At the surface, a trailing cold front will plunge south through the High Plains and Rockies. Post-frontal easterly flow, along with increasing synoptic scale ascent ahead of an amplifying trough approaching from the west, is expected to support widespread mountain snows across the Colorado and northern New Mexico ranges by late Tuesday, with locally heavy accumulations possible by early Wednesday. The potential for heavy snow is expected to increase across southern Colorado and northern New Mexico and spread south on Wednesday. As the previously noted upper trough continues to amplify and swing east, enhanced northeasterly flow on the backside of a low level wave developing over the southern Plains will help support the development of heavy snows spreading south through the central into the southern New Mexico ranges Wednesday night into Thursday morning. 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. ...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... Days 2-3... Wednesday morning is expected to mark the onset of what will likely become a prolonged, multi-round winter weather event impacting a large portion of the central U.S. 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. Precipitation will continue to develop and propagate northeast across the region into late Wednesday as another area of organized precipitation develops back to the southwest. As the upper trough in the west continues to move east across the Southwest, 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. By early Thursday, these two events are expected to combine to produce a long swath of snow accumulations of 4 inches or more -- extending from northeastern Oklahoma and eastern Kansas to Lower Michigan. Within this area, accumulations of a foot or more are possible. Latest WPC probabilities indicate that accumulations of a foot or more are most likely from east-central Kansas to northwestern Indiana. South of the heavier snow, a wintry mix, including freezing rain, will likely impact areas from North Texas to central Ohio. 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 and southern Illinois. Pereira ~~~ 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.