Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 359 AM EST Sat Feb 13 2021 Valid 12Z Sat Feb 13 2021 - 12Z Tue Feb 16 2021 ...Mid Atlantic... Day 1... A series of weak disturbances embedded within moist, southwesterly flow aloft and interacting with shallow cold air east of the mountains, will encourage freezing rain, with significant ice accumulations likely across portions of central Virginia into southern Maryland on Saturday. ...Pacific Northwest... Day 1... As arctic air remains entrenched, another shortwave trough will slide southeast across the region later today. More snow is expected across the lowlands, including the Seattle and Portland metro regions, where an additional accumulations of at least an inch or two is likely. Heavy accumulations are likely for portions of the Cascades, with additional accumulations of 1-2 feet expected across the higher elevations of the southern Washington and Oregon Cascades. ...Intermountain West and Rockies... Day 1... The previously noted shortwave is forecast to move progressively southeast on Saturday -- supporting precipitation spreading quicky east of the Cascades through the northern Intermountain West into the northern and central Rockies Saturday morning, before reaching into northern and central Arizona and the southern Rockies by late in the day. Large-scale ascent supported in part by left-exit region upper jet forcing, will contribute to widespread precpitation across the region, including locally heavy mountain snows. A low level wave developing over Utah and moving southeast into Colorado along the left-exit region of the upper jet, is expected to support a period of enhanced upslope flow and convergence -- raising the potential for heavy snowfall rates across the central and southern Utah, into the southwestern Colorado and northern New Mexico ranges late Saturday into Sunday. By early Sunday, local snowfall accumulations of a foot or more are likely across those areas. ...Central and Southern Plains to the Lower Mississippi Valley... Days 1-2... Supported by low level easterly flow and an upper jet couplet, snow will begin to spread east of the central Rockies into the High Plains Saturday night, with accumulations of 4-inches or more likely along the Kansas-Colorado border by midday Sunday. As the upper trough begins to move east across the southern Rockies, favorable upper jet forcing, along with a low level baroclinic zone will support heavy snows developing farther across portions of Oklahoma and northern Texas on Sunday. As the upper trough continues farther east, drawing colder air across the southern Plains, a wintry mix, including accumulating snow is forecast to extend as far south as South Texas Sunday night. Sleet and freezing rain is likely to develop along the Texas coast and across eastern Texas into the lower Mississippi valley Monday morning, with significant ice accumulations possible across eastern Texas into northern Louisiana and western Mississippi. ...Southern Plains to the Northeast... Day 3... Beginning late in the Day 2 period and continuing into Monday, areas of light to moderate snow and freezing rain are expected to move northeast along a low-to-mid level baroclinic zone extending form the Ohio valley through the northern Mid Atlantic and Northeast. Meanwhile, organized moderate to heavy precipitation developing late in the Day 2 period along the right-entrance region of the upper jet and near a low-to-mid level frontal zone will continue to move east from eastern Texas and across the lower Mississippi valley, with significant ice accumulations possible from southeastern Texas, through Lousisana into Mississippi. A stripe of heavier snow is expected to develop farther to the north from northeastern Texas to western Tenneesse and Kentucky Monday morning. This area of organized heavier snow is expected to translate northeast through the Ohio valley and into the Lower Great Lakes region Monday night into early Tuesday. South of the heavier snow, a stripe of significant ice accumulations is expected to spread from the Tennessee valley through the central Appalachians and into the northern Mid Atlantic, southern New York and New England Monday night into Tuesday morning. Pereira