Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 413 PM EST Fri Jan 14 2022 Valid 00Z Sat Jan 15 2022 - 00Z Tue Jan 18 2022 ...Mid Mississippi Valley... Day 1... As an upper level shortwave continues to amplify and dive southeast, an area of ongoing snow across southern Minnesota and Iowa will continue to shift farther south through the evening, with locally heavy amounts possible across portions of southern Iowa into northern Missouri. Low-to-mid level frontogenesis overlapped by favorable upper forcing is expected to support moderate to heavy snowfall rates. Latest HREF guidance indicates snowfall rates reaching over an inch/hour across portions of southern Iowa into northern Missouri this evening and overnight. WPC probabilities indicate that accumulations of 4 inches or more are likely, with 8 inches or more possible. ...Ozarks to the Tennessee and lower Ohio Valleys... Day 2... As the developing upper low continues to dig south and colder air spills in, rain changing to snow is expected across central into southern Missouri overnight Saturday into Sunday. Models continue to show a signal for light to moderate snow developing up on the northwest side of the deformation zone. Snow is expected to initially impact the Ozark region on Saturday before shifting east across the Mid South into the Tennessee and lower Ohio valleys. Still a fair amount of uncertainty across this area, with some ensemble guidance still showing the potential for heavy amounts extending farther south and west than the general consensus of the deterministic guidance across portions of Arkansas, western Tennessee, and northern Mississippi. However, confidence has increased in the threat for heavier amounts farther east, impacting portions of Middle Tennessee into eastern Kentucky. As the upper low is expected to swing east from the lower Mississippi Valley into the Southeast, guidance shows the associated deformation zone pivoting across the region, with potentially significant impacts as rain changes to snow on Sunday. Probabilities for accumulations of 4 inches or more have increased and are now above 50 percent across portions of Middle Tennessee, including the Nashville area. ...Eastern Seaboard from Georgia to Maine... Days 2-3... There remains a strong signal for significant ice accumulations across portions of the Carolinas and heavy snow extending north from the southern and central Appalachians into the interior Northeast. As the low over the Southeast continues to track east, low-to-mid level frontogenesis will support precipitation spreading north ahead of the system from the Southeast into the southern Appalachians and Piedmont on Sunday. At the surface, a strong surface high will remain centered over the Northeast, with a pronounced surface ridge extending south. This will set the stage for a significant icing event over the Piedmont, with heavy snow accumulations expected over the southern Appalachians. With the wedge expected to remain in place through much of the day on Sunday, significant ice accumulations are likely over the Piedmont, with light ice accumulations extending out into the coastal plains. WPC probabilities indicate ice accumulations of 0.10 inch or more are likely from northeastern Georgia into the southern Virginia Piedmont. Within this area, locally heavier accumulations of 0.25 inch or more can be expected. This includes the Charlotte metro into central North Carolina, where WPC probabilities of accumulations of 0.25 inch or more are around 50 percent or greater on Sunday. Farther to the west, heavy snow is likely for the mountains, with WPC probabilities indicating accumulations of 8 inches or more are likely for the western North Carolina mountains. By late Sunday, the low is expected to begin its rapid track north along the east coast -- reaching the northern Mid Atlantic and Northeast Monday morning and northern New England by late in the day. General consensus of the models continues to indicate snow changing to rain for the major cities along the Mid-Atlantic-Northeast I-95 corridor, with heavy snow accumulations farther west -- centering along central Appalachians into the interior Northeast. WPC probabilities indicate that widespread totals of 6-12 inches are likely, with locally heavier amounts expected across the region. Bolstered by a period of lake enhancement behind the departing system, some of the heaviest amounts are expected to center across western and central New York, where WPC probabilities show some of the greater potential for accumulations of a foot or more by late Monday. Pereira ~~~ Key Messages for Winter Storm Affecting the Mid Mississippi Valley and Ozark Region to the Eastern U.S. January 15-17 ~~~ -- Heavy snow is expected across portions of the Mid-South and Tennessee Valley. Narrow, localized areas of higher snow totals in excess of 6 inches are possible, but there remains uncertainty in the location and potential of these higher snow bands. -- Ice accumulation is likely from northeast Georgia through southern Virginia. The most damaging and significant icing potential is across the Piedmont of the Carolinas and this is likely to result in dangerous travel, power outages, and tree damage. -- Heavy snow is expected in and near the Appalachians, and across much of the interior Northeast and New England, well inland from the major cities. Significant snow totals are likely across western North Carolina northward to western New York. -- Along the Atlantic coastline, strong winds and coastal flooding are likely. Some locations may reach moderate flood levels, with inundation affecting some coastal roads and structures.