Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 413 AM EDT Mon Mar 25 2024 Valid 12Z Mon Mar 25 2024 - 12Z Thu Mar 28 2024 ...Southern Rockies... Day 1... An inverted 500mb trough over the Southern Rockies will be the focus for additional heavy snow today. The Sangre De Cristo and eastern San Juans both sport high chances (>70%) for additional snowfall totals >8" with the tallest peaks of the Sangre De Cristo in northern New Mexico even having moderate-to-high chances (50-70%) for >12" snowfall accumulations through Monday afternoon. The axis of moisture and lift associated with this upper trough will even result in heavy snow over the Gila Mountains in eastern Arizona. WPC PWPF shows moderate chances (40-60%) for snowfall accumulations >8" through Monday evening. The 500mb trough will eject east into the Southern Plains Monday night, thus all but concluding the lingering periods of snow by Tuesday morning. ...Northern Plains & Upper Midwest... Days 1-2... The major winter storm will be well underway with the worst impacts being felt from the central High Plains on north to north-central Minnesota. The deformation axis on the northern and western flank of the storm will be capable of producing 1-2"/hr snowfall rates to go along with wind gusts that are exceeding 40 mph in northwest Kansas, central Nebraska, and southeast South Dakota. Farther east, the impressive 850mb WAA in the Upper Mississippi Valley that was in part responsible for the heavy snowfall overnight will lead to a burgeoning warm nose at low levels that causes snow to changeover to a wintry mix this morning in southern Minnesota, northern Wisconsin, and the Michigan U.P. By this afternoon, any lingering wintry mix is expected to transition over to plain rain. Meanwhile, the storm will continue its trek northeast into the Upper Mississippi Valley Monday evening with heavy snow enveloping eastern South Dakota, northern Minnesota, and the Minnesota Arrowhead. Snow will continue to fall heavily over north-central Minnesota Monday night with some residual snow as far south as eastern Nebraska and northern Kansas as a TROWAL pivots overhead. By Tuesday morning, the low will be tracking into northern Wisconsin with heavy snow across northern Minnesota and a mix of heavy snow/wintry mix along the Minnesota Arrowhead. The storm will then move over the U.P. of Michigan Tuesday afternoon, then finally into southern Ontario Tuesday night. Snow will continue to fall across northern Minnesota and portions of far northern Wisconsin and the western Michigan U.P. Heavy snow will effectively come to an end by Wednesday morning with just lingering snow showers along the Minnesota/Canada border and along the northern coast of the Michigan U.P.. WPC PWPF shows moderate-to-high chances (50-70%) for additional snowfall >6" from north-central Nebraska and eastern South Dakota to far southeast North Dakota, northern Minnesota, and the Minnesota Arrowhead. South-central South Dakota and the Minnesota Arrowhead even show low chances (10-30%) for additional localized snowfall amounts >8". Farther southwest, WPC PWPF shows moderate- to-high chances (50-70%) for additional snowfall totals >4" in southwest Nebraska, northwest Kansas, and southeast Colorado. Nebraska and northwest Kansas, in particular, could contend with blizzard conditions due to prolonged high wind gusts and significantly reduced visibilities. ...Pacific Mountains Ranges... Days 2-3... Outside of some diurnally driven snow showers and weak onshore flow in the Pacific Northwest through Tuesday night, little in the way of heavy snowfall is likely to occur for many of the mountains ranges along the West Coast. That finally changes by early Wednesday morning as the next Pacific storm system approaches and directs a slug of Pacific moisture first at the Pacific Northwest, then into the Northern California ranges and interior Northwest ranges Wednesday night. The IVT is a quick mover but a fairly potent IVT sporting values >400 kg/m/s just off the California coast. Overall, the peak of the IVT tracking into northern California Wednesday afternoon is likely to top the 97.5 climatological percentile, supplying not only abundant moisture to the region but strong upslope enhancement (especially in the Sierra Nevada). Snow levels in the Sierra Nevada will initially start out as high as 6,500ft, but gradually fall to 5,000ft by Thursday morning as the cold front pushes through. Farther north, snow levels will start out around 5,000ft in the northern California ranges (Salmon/Siskiyou/Trinity) and closer to 4,500ft in the OR/WA Cascades, but those too will fall an additional 2,000ft by Thursday AM. Latest WPC PWPF shows high chances (>70%) for snowfall amounts >8" in the Northern Sierra Nevada >6,000ft and in the northern California ranges, while only the volcanic peaks of southern Washington and the Olympics sport similar high chances for >8" of snowfall through early Thursday morning. Some snow will spill over into the Blue Mountains and the Boise/Sawtooth late Wednesday night into Thursday with low-to-moderate chances (30-50%) for snowfall totals >6" through early Thursday morning. Mullinax ***Key Messages for Plains-Upper Midwest Winter Storm*** --A high-impact winter storm unfolding A powerful storm system will impact the Northern/Central Plains into the Upper Midwest through Tuesday. Periods of snow and gusty winds will continue from the Central Plains to northern Minnesota, along with some sleet and freezing rain in parts of the Upper Mississippi Valley. --Widespread heavy snow expected Snow accumulating at rates of 1-2"/hr in heavier bands are expected from central Nebraska and eastern South Dakota to northern Minnesota. Additional snowfall totals between 6-12" are forecast from central Nebraska to northeastern Minnesota. --Hazardous impacts due to snow, snow load, and wind Heavy snow and gusty winds approaching 50 mph will produce blizzard conditions with near zero visibility into Tuesday morning. Travel could be nearly impossible at times. Power outages and tree damage are likely in some areas due to the heavy and wet snow combined with icing and strong winds.