Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 424 PM EDT Tue Apr 12 2022 Valid 00Z Wed Apr 13 2022 - 00Z Sat Apr 16 2022 ...Northern Rockies through the Northern Plains... Days 1-3... ...Significant and potentially historic blizzard continues for portions of the Northern Plains... A historically significant, high-impact blizzard will continue across the northern Plains through Wednesday, producing record-breaking multi-day snowfall totals for portions of eastern Montana to central North Dakota. An amplified mid-upper level disturbance emerging eastward from the northern Rockies will acquire negative tilt, and this will support a well developed surface low that will track from eastern Nebraska to Wisconsin through midday Wednesday. Meanwhile, a rather pronounced trough axis will extend northwest of this low, with a secondary low developing near the ND/MN border late Wednesday in combination with a trowal type feature. Strong low-to-mid level frontogenesis overlapped by coupled upper jet forcing northwest of the low will support the development of widespread heavy snow from eastern Montana to North Dakota. The latest high-res guidance suite continues to strongly favor redevelopment of mesoscale snowfall bands through tonight, and these are resulting in enhanced snowfall rates on the order of 1-2+ inches per hour developing across much of central and western North Dakota, creating white-out conditions when coupled with the strong winds. The potential for locally heavy snow will persist into Wednesday as the upper low continues to deepen and slowly drift east across the northern Plains. Even with some uncertainty in the finer mesoscale details, the WPC probabilities indicate that by late Wednesday, accumulations of a foot or more are likely, with accumulations over two feet possible from the southern Montana-North Dakota border northeastward into north-central North Dakota. In addition to the heavy snow, strong and gusty winds exceeding 40 mph, supported by a tight pressure gradient on the northwest side of the low, is expected to produce widespread blizzard conditions with significant blowing and drifting snow. By late Wednesday, the majority of the event should be over for North Dakota as the main moisture axis lifts northward across Canada. However, gusty winds and some additional light to moderate snows are likely to continue into Thursday with wrap-around moisture remaining in place south of the main surface low. Across western into north-central North Dakota, storm total amounts in excess of two feet, with locally heavier amounts approaching three feet, are possible by the time the event finally concludes. ...Pacific Northwest... Days 1-3... The 12Z model guidance suite continues to indicate another closed low developing offshore and then moving inland across Oregon and Washington during the day on Wednesday, with shortwave energy lingering in place through early Thursday. There will be enough moisture and deep layer ascent to support periods of organized moderate to locally heavy snow showers across western Oregon and northwestern California. Several inches of additional snow accumulation is likely for the Oregon Cascades, with some of the highest elevations receiving over a foot of snow by early Thursday. Given the anomalous 500 mb heights associated with this pattern and steep lapse rates, snow levels are expected to remain low with some minor accumulations possible across the valley locations, with locally heavy amounts possible across the higher elevations of the coastal ranges. Surface temperatures and snowfall rates will be the key determining factors regarding accumulation below 1000 feet, with wetbulb temperatures likely above freezing near the surface. Northern portions of the Sierra can also expected some welcomed late season snowfall as the moisture plume slowly settles southward. For Days 1-3, the probability of 0.10 inch or more of ice is less than 10 percent. Hamrick/Jackson ~~~Key Messages for April 12-14 Blizzard~~~ --A blizzard will continue to impact much of the northern Plains through Thursday. --The combination of heavy snow and strong wind gusts will produce dangerously low visibility with significant blowing and drifting of snow. --Travel will be remain difficult to impossible, and widespread power outages and tree damage are expected. Significant impacts to livestock are also possible. --Snowfall is likely to reach record levels in parts of eastern Montana and western and central North Dakota, with maximum storm total snowfall of three feet possible.