Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 455 PM EDT Sun Apr 02 2023 Valid 00Z Mon Apr 03 2023 - 00Z Thu Apr 06 2023 ...Great Basin and Central Rockies to the Upper Midwest... Days 1-3... ...A powerful storm system producing heavy snow and strong winds is likely to impact a large portion of the central Rockies and north-central U.S.... Not much change to the large-scale picture, with models continuing to show a powerful winter storm evolving over the Intermountain West and central Rockies on Monday, before lifting northeast into the north-central U.S. Tuesday into Wednesday. This system is likely to spread widespread heavy snow and produce strong, gusty winds across the region. This system is expected to develop Monday as a well-defined shortwave embedded within a broader scale trough digs southeast from the Pacific Northwest into the Great Basin and Southwest by late in the day. Model consensus continues to show 500mb standardized anomalies of -2.5 to -3 translating east across the Great Basin into the central Rockies as the trough amplifies and an upper low closes off over the region Monday night. Moderate to heavy snow is expected to initially develop along a strong low-to-mid level baroclinic zone settling southeast behind an impressive surface low organizing over eastern UT on Monday. This is likely to produce heavy accumulations over the UT ranges. Meanwhile, strong low level easterly flow developing north of a strong front east of the mountains, will support the development of moderate to heavy snows over the central High Plains back into the south-central Wyoming mountains. By late Monday, WPC probabilities indicate widespread snow amounts of 6 inches, with locally higher totals likely. WPC guidance indicates the heaviest amounts through late Monday are likely to center over the northern UT ranges and along the Laramie Mountains in southeastern Wyoming. By late Monday and continuing through Tuesday, the closed upper low developing over the Great Basin-central Rockies is forecast to lift northeast into the High Plains, sending an intensifying surface low east-northeast from eastern Colorado across the central Plains. Strong upper forcing combined with low-to-mid level frontogenesis will support moderate to heavy snow developing on the northwest side of the surface low, with heavy accumulations likely from southeastern Wyoming to central South Dakota by late Tuesday. WPC probabilities indicate that snow accumulations of a foot or more are likely across this area late Monday to late Tuesday. In addition to the heavy snow threat, strong gusty winds afforded by a tight pressure gradient will contribute to hazardous conditions. Overall, models have remained in fairly good agreement with the larger scale pictures. Differences remain in the finer details, especially along the southern edge of the heavy snow axis, where marginal temperature profiles contributing to a wintry mix may limit snow accumulations from the southern Nebraska Panhandle into southeastern South Dakota. Moderate to heavy snow is likely to continue through late Tuesday into Wednesday across portions of the northern Plains into the Upper Midwest as the low continues to deepen and lift northeast. Heavy snow accumulations during the period are likely to extend from northeastern South Dakota northeastward through eastern North Dakota and northwestern Minnesota. Snows are expected to begin to diminish, however strong winds will continue as the low begins to lift into western Ontario Wednesday evening. Storm total amounts of a foot or more are likely to extend from the Utah mountains to northwestern Minnesota, with accumulations exceeding two feet in some locations. Please see our key messages below for additional highlights regarding this storm. ...Pacific Northwest... Days 1-3... Energy embedded within northwest flow on the backside of the broader-scale trough is expected to produce periods of snow Monday and Tuesday. Snow levels are forecast to fluctuate, but remain largely below at or below 1000 ft through the period. Light accumulations are expected in the lowlands of eastern Washington, Oregon, and northwestern California, with heavy accumulations of a foot or more likely over the Oregon Cascades. Snow levels are forecast to rebound with the approach of warm front and light precipitation on Wednesday. Pereira ...Key Messages for April 3-5 Winter Storm... --Widespread Heavy Snow Totaling Over One Foot A major winter storm is expected to produce over a foot of snow from the Central Rockies to the Northern Plains, challenging some April snow records in the Dakotas and northwest Minnesota. Localized 24â€+ totals are possible from southeast WY to central SD. Avalanches and significant impacts from snow load are possible across portions of Utah. --Blizzard Conditions in the Northern Plains Strong winds and heavy snow will create whiteout conditions Tuesday and Wednesday, causing dangerous to impossible driving conditions and considerable disruption to daily life. --Life Threatening Cold for Anyone Stranded Wind chills will fall to near or below zero during the blizzard in the Northern Plains, which could be life-threatening to anyone stranded. --Damaging Winds From the Southwest to the Midwest Widespread gusts in excess of 50 MPH will spread from the Southwest and Four Corners Monday, to the Plains Tuesday, and Upper Midwest Wednesday. Power outages, wind damage, and blowing dust, even outside of thunderstorm activity, are likely.