Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 445 AM EST Wed Feb 02 2022 Valid 12Z Wed Feb 02 2022 - 12Z Sat Feb 05 2022 ...Pacific Northwest... Days 1-3... Two shortwaves, one on Thursday and another on Friday, will drop southeast into the Pacific Northwest, separated by brief shortwave ridging Thursday night. The trailing shortwave is the stronger of the two, but both will be accompanied by diffluence at the leading edge of a Pacific jet streak to enhance deep layer ascent and spread moisture inland. The shortwaves will be embedded in otherwise mostly confluent flow, so the duration of forcing to produce snowfall should be limited as each shortwave is expected to be transient. However, briefly heavy snow is likely in the Washington Cascades both days 1 and 3, where WPC probabilities for 6+ inches peak above 40 percent. Snow levels during this time will be rather low, about 2000 ft on Day 1 and climbing to around 3000 ft by Day 3. This suggests that many of the Cascade Passes will also receive accumulating snow, with more than 6 inches likely at Snoqualmie Pass. ...Southern Rockies through the Central Plains and into the Northeast... Days 1-3... ...Several rounds of heavy wintry precipitation likely as a large scale system expands across the eastern CONUS... A large scale and multifaceted winter storm is expected to produce a variety of winter weather hazards through midweek, including heavy snows extending from the southern Rockies to the interior Northeast, and significant ice accumulations from portions of the southern Plains, through the Ohio Valley and into the Northeast. The first phase of this event is now well underway, with widespread light to moderate snow continuing to develop and spread northeast from the central Plains to Lower Michigan. Large scale ascent afforded in part by a coupled upper jet, along with strong low-to-mid level frontogenesis, will help sustain this developing axis of snow as it continues to shift northeast through the day -- generating a swath of moderate to heavy accumulations from the mid Mississippi Valley to southern Lower Michigan. South of the heavier snow area, a wintry mix, including freezing rain, is likely to develop this morning across southern Missouri and spread east into the lower Ohio Valley today. Meanwhile farther to the southwest, as an amplifying upper trough approaches from the northwest, low level easterly flow along the western edge of a sharp ridge nosing south through the high plains will support heavy snows developing and shifting south along the southern Colorado and New Mexico ranges. By early Thursday, accumulations of 8-12 inches, with locally heavier amounts, are likely from the San Juan and Sangre de Cristo to the Sacramento mountains. Farther to the east, a lingering low level boundary will help support developing snows across eastern Colorado into western Kansas. High snow-to-liquid ratios well within the arctic air is expected to produce widespread light and fluffy snows across the region. By later today, as the upper trough continues to drop southeast, organized precipitation is expected to develop across the southern Plains. Right entrance region upper jet forcing along with strong low-to-mid level frontogenesis will support the development of moderate to heavy precipitation across portions of the region. This will include an area of widespread light-to-moderate and potentially locally heavy snow from Northwest Texas to central Missouri overnight. South of the heavier snow, a wintry mix, including freezing rain, will spread south into the Texas Hill Country and east from southeastern Oklahoma into the Ohio Valley. During the day on Thursday, moderate to locally heavy snows are expected to gradually shift northeast from the mid Mississippi Valley to the lower Great Lakes, before moving across northern New York and northern New England overnight. South of the heavier snow, an icy transition zone will persist, with widespread freezing rain expected from eastern Oklahoma and Texas to central New England. By late Friday, the event is expected to finally wind down as the associated front moves off the Northeast/Mid-Atlantic coast, but not before a few more inches of snow is expected to occur across northern to central New England, while a mix of sleet and freezing rain drops southeast, potentially impacting the the major cities along the I-95 corridor. WPC probabilities continue to show widespread event totals of 4-8 inches of snow extending from Kansas, Oklahoma and Northwest Texas to northern New England. Within this area, locally heavier accumulations are most likely from central Illinois to northern New England. Ice accumulations of 0.10-0.25 inch are likely from the Texas Hill Country through the Ohio Valley and into portions of central Pennsylvania and Upstate New York. Locally heavier ice accumulations are most likely from Mid-South through the Ohio Valley. Pereira/Weiss ~~~ Key Messages for Feb 1-3 Winter Storm ~~ -- A large and significant winter storm will impact much of the central U.S., bringing a variety of winter weather hazards including heavy snow, sleet, and freezing rain. -- The storm will be prolonged with several rounds of winter weather lasting through Thursday for portions of the central U.S. before shifting to the interior Northeast. -- Heavy snow is expected over the southern Rockies and from the south-central Great Plains through the eastern Great Lakes and interior Northeast. A corridor of heavy ice accumulation is likely from Texas through the Ohio River Valley. -- Locations impacted by snow and/or ice are expected to have temperatures remain below freezing, and well below average, for at least a couple days after the wintry precip ends. -- Plan now for prolonged hazardous winter weather conditions and disrupted travel.