Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 401 PM EST Thu Jan 13 2022 Valid 00Z Fri Jan 14 2022 - 00Z Mon Jan 17 2022 ...North to Central Great Plains/Upper to Mid Mississippi Valley... Days 1-2... An open wave trough associated with the remnants of an upper low moving currently moving into the Pacific Northwest is expected to phase with a northern stream trough dropping southeast from western Canada -- forming an amplified positively-tilted trough over the central U.S. on Friday. By early Saturday, models show a closed low developing over the central Plains before digging farther south into the southern Plains late in the day. Models continue to indicate strong low-to-mid level frontogenesis and favorable upper forcing ahead of the northern wave supporting the development of moderate to heavy banded snowfall moving southeast from eastern North Dakota overnight Thursday, into eastern South Dakota and southwestern Minnesota by Friday morning. Moderate to heavy snow bands are expected to shift farther south into Iowa on Friday before a comma-head associated with the developing upper low begins to evolve Friday evening. HREF guidance continues to show the potential for snowfall rates of at least 0.5 inch/hr shifting southeast across central and eastern North Dakota into eastern South Dakota and southwestern Minnesota overnight into early Friday. During the day, heavy snow is expected to gradually shift farther southeast into Iowa. WPC probabilities continue to show snow accumulations of 4 inches or more are likely along a narrow axis extending from central North Dakota to northern Missouri during the Days 1 and 2 periods. There is also significant potential for locally heavier amounts of 8 inches or more, especially from southeastern North Dakota into central Iowa during this time. Along the western edge of the heavier snow, a wintry mix, including freezing rain is expected. While widespread heavy ice accumulations are not expected, WPC probabilities continue to indicate that at least some light accumulations are likely from central North Dakota to eastern Nebraska and western Iowa. ...Ozarks to the Tennessee and lower Ohio Valleys... Days 2-3... Upper low closing off over the central Plains on Saturday is forecast to dig farther southeast into the lower Mississippi Valley by late in the day before pivoting eastward toward the Southeast. From the Ozark region eastward into the lower Ohio and Tennessee Valleys, expect rain changing to snow late Saturday into early Sunday. Models have been showing increasing potential for the development of moderate to perhaps locally heavy snows across this region. As the upper low pivots east, favorable upper jet forcing overlapping low-to-mid level frontogenesis may support a window for heavy snows to develop. From the Ozarks eastward into Tennessee and Kentucky, WPC probabilities for accumulations of 4 inches or more and under 50 percent in most locations, however would not be surprised to see those numbers increase in subsequent runs. ...Southeast to the Mid-Atlantic... Day 3... A classic cold air damming scenario is expected to unfold, resulting in significant icing for portions of the Mid Atlantic Piedmont and heavy snow for the southern to central Appalachians. As the upper low continues to swing east, assuming a negative-tilt over the Southeast, strong surface high pressure will remain in place over the Northeast. A well-defined surface ridge will remain locked in east of the mountains as low pressure develops along the Southeast coast. By late Sunday, snowfall accumulations of 8-12 inches are likely, with locally heavier amounts expected across the mountains of western North Carolina. Ice accumulations of 0.1 inch or more are expected along the Piedmont across portions of northern Georgia and along much of the Carolina Piedmont. Locally heavy ice accumulations of 0.25 inch or more can be expected, especially across portions of the Carolinas. Pereira ~~~ Key Messages for Winter Storm Affecting the Northern Plains to Upper Midwest January 14-15 ~~~ -- A fast-moving winter storm will drop southward across the Northern Plains tonight, continuing through the Upper Midwest and into the Mid-Mississippi Valley Friday night. -- A swath of heavy snow exceeding 8 inches is expected with this system from eastern North Dakota through southern Iowa. Snowfall rates may reach 1"/hr at times. -- This snow will combine with gusty winds to produce slippery, snow covered roads and significantly reduced visibility. Travel will likely become hazardous dangerous at times. ~~~ Key Messages for Winter Storm Affecting the Mid Mississippi Valley and Ozark Region to the Eastern U.S. January 15-17 ~~~ -- Confidence is increasing that a significant winter storm will create considerable impacts from this weekend into early next week. There is still uncertainty on the details, so check back on the forecast for updates. -- Heavy snow is expected from the Mid Mississippi River Valley, to the Appalachians, and well inland from the major cities, leading to difficult travel. There remains potential for heavy snow getting into the I-95 metropolitan areas. -- Significant icing is likely in parts of the Carolinas, and adjacent parts of northeast Georgia and central Virginia. This will likely lead to power outages and damage to trees. -- Close to the immediate Atlantic coastline, strong winds and coastal flooding will be possible.