Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 337 AM EST Thu Mar 10 2022 Valid 12Z Thu Mar 10 2022 - 12Z Sun Mar 13 2022 ...Southern Rockies to Central Plains... Day 1... Shortwave trough energy dropping through the Intermountain West this morning will reach the Four Corners region by 12Z Friday. A pair of surface fronts slowly moving through the region as well combined with the impressive height falls and large scale forcing for ascent will continue the widespread moderate to locally heavy precipitation today. The bulk of the heaviest snow amounts will be across the favored terrain areas where WPC probabilities for 4 inches are moderate to high, particularly for the San Juans Ahead of it, height falls and upper divergence will bring a large area of forcing for ascent. This will bring an area of moderate to locally heavy precipitation for the San Juans and Sangre De Cristos. Across the Central Plains this morning, a zone of mid-level frontogenesis and an inverted trough across Kansas will continue to support a corridor of moderate to locally heavy snowfall through mid-day. Additional accumulations will be focused on eastern KS to western MO where upwards of 2-4" are expected. ...Pacific Northwest... Day 3... A compact shortwave trough closing off over northwest Washington late on D3 will push a narrow plume of moisture into the region. IVT values approach moderate levels and the forcing for ascent combined with upslope flow supports widespread precipitation during the back half of the period. Snow levels generally 3000-6000+ ft will confine the greatest snow accumulations to the higher peaks and the latest WPC probabilities are high for 4" across the WA Olympics and Cascades with a slight to moderate signal for 8-12"+ totals. ...Ohio Valley to Mid-Atlantic and Northeast... Days 2-3.. A pair of shortwave troughs within the northern and southern streams will approach the central U.S. Friday into Friday night and intensify early Saturday as phasing commences. The combined trough axis then takes on a strong neutral tilt Saturday into Saturday night leading to impressive forcing for ascent downstream. Strong mid to upper divergence and a coupled jet streak over the East Coast will help deepen a surface low originating from the Southeast as it moves through the Mid-Atlantic and eastern New England. Strong CAA on the backside of the deepening low will result in a changeover from rain to snow and just to the northwest/north of the low center, a corridor of heavy snow is likely. Within this snow band, snow rates are likely to be 1-2"/hr and this will likely overcome any warm ground temperatures at its peak. With upwards of 0.75 to 1.5" of QPF, significant snow accumulations are possible, particularly for the interior Northeast. WPC probabilities for D2 are moderate (40-50%) for TN and reach above 60 percent for much of central/eastern KY northeast through eastern OH, western WV toward western NY. Into the terrain of Upstate New York and Northern New England, this event is likely to be all snow, and will be heavy at times. WPC probabilities are above 90% for 4 inches, as high as 50-60% for 12+ inches in the Adirondacks. An impactful swath of double-digit snow totals is likely across much of the interior Northeast. Taylor ~~~ Key Messages for Tennessee Valley through the Northeast Winter Storm ~~~ -Confidence continues to increase in a significant and impactful winter storm for portions of Tennessee and Ohio Valleys through the interior Eastern U.S. late Friday through Saturday. -Snow rates greater than 1â€/hr, gusty winds, and severely reduced visibility will make for hazardous to difficult driving conditions and travel at times, particularly across the interior Northeast. -The greatest accumulations are likely across portions of the interior Northeast where totals in excess of 12†are likely. -In the wake of the storm system, much colder air will spread across the Southeast and Mid-Atlantic with lows likely below freezing along the Gulf Coast and northern Florida Sunday morning.