Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 254 PM EST Fri Jan 21 2022 Valid 00Z Sat Jan 22 2022 - 00Z Tue Jan 25 2022 ...Western/Southwestern U.S... Days 1-3... Strong mid-level shortwave trough moving through the Great Basin will dig south-southeastward and close off over the Desert Southwest tonight. This weekend, the closed low is forecast to dip into northern Mexico and turn east, eventually pushing into far west Texas by the end of Day 3 (12Z Mon) as it starts to weaken. Sufficient moisture and forcing is favored over Colorado day 1, coupled with orographic enhancement, yielding locally heavy snowfall accumulations for areas of the central Rockies with as much as 6 to 12 inches of new snowfall and isolated heavier amounts, especially over the Sangre De Cristo range. Nearer to the track of the upper low, more favorable dynamics will capitalize on limited moisture to produce a few inches of snow over the higher peaks in eastern Nevada. By days 2 and 3, sufficient forcing may allow for some light snowfall accumulations to occur over the Mogollon Rim of AZ as the upper low turns toward the east. ...Southern Mid Atlantic... Day 1... Strong 1040+ mb high pressure over Quebec this afternoon continues to funnel an Arctic airmass down the East Coast wedged along the spine of the Appalachians. Southern stream energy lifting northeast from the northern Gulf of Mexico and a strong 150+ jet streak over the Mid-Atlantic will lead to banded precipitation breaking out over portions of the Southeast and Carolinas this afternoon through early Saturday, peaking between 00Z-09Z. Soundings support mostly snow across the Piedmont of SC/NC while a wintry mix to significant ice accretion is expected along the coastal plain region toward the immediate coastline. The last couple cycles of the global and hi-res guidance have trended wetter and a bit further west with the banding setup and the WPC deterministic and PWPF followed as well. A stripe of 2-4" appears likely from portions of the SC Piedmont through central NC, enhanced by the approach of the upper vort max toward 06Z and then across northeast NC and far southeast VA localized 4-6" totals are expected. This lines up well with the latest WPC probabilities for 4 inches which reach near 50 percent locally. Ice accretion up to 0.20" is expected south/southeast of that axis and could potentially be significant resulting in dangerous travel and scattered power outages. ...Upper Midwest/Great Lakes... Days 1-3... Positively titled trough axis from the Tennessee Valley to the Great Lakes today will be replaced by fast cyclonic flow and deeper upper troughing over much of the Great Lakes and East Coast tonight through early next week. Several embedded shortwaves will swing through the flow, the first pushing through the northern Plains and Upper Midwest tonight into Saturday. A second shortwave passes through the Upper Midwest late Saturday into Sunday morning while a third wave arrives for Monday across the northern Plains. The combination of modest lift and forcing and the cold airmass supporting SLRs in the 15-20:1 range will likely bring swaths of a few fluffy inches oriented northwest to southeast of the low track. Downwind of the Great Lakes, favored snow belt regions will see enhanced snow totals. In total, amounts could reach 4-6 inches across portions of MN/WI while the favored LES snow belt areas could exceed 6-8" with localized totals near 1 foot. ...Eastern Massachusetts... Day 1... Favorable northeast flow of the Atlantic into the very cold airmass will continue to support locally moderate ocean effect snows across portions of eastern Massachusetts, generally south/southeast of Boston and over Cape Cod. Some localized totals in excess of 2 inches will remain possible through Saturday morning before the flow becomes less favorable and QPF ends. Fracasso/Taylor ~~~ Key Messages for Winter Storm Impacting Portions of the Southeast and Mid-Atlantic Jan 20-22 ~~~ -- Snow, sleet, and freezing rain will spread across areas of the Southeast through the southern Mid-Atlantic states through early Saturday. -- Significant ice accumulations are expected in parts of the Carolinas, resulting in dangerous travel conditions and scattered power outages. -- Moderate to locally heavy snow is forecast from northeastern North Carolina through the southern DelMarVa Peninsula.