Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 401 PM EST Tue Feb 22 2022 Valid 00Z Wed Feb 23 2022 - 00Z Sat Feb 26 2022 ...Southwest U.S.... Days 1-2... An amplifying shortwave trough currently off the OR/CA border will dig the main western trough into southern CA into Wednesday before ejecting east across the Four Corners Wednesday night and onto the southern Plains early Thursday. Pacific moisture will continue to stream inland ahead of the trough which along with the height falls will allow snow levels to decrease, setting up heavy snow through Desert SW terrain. Heavy snow is expected above about 1500ft for the southern Sierra Nevada, 3000ft for the southern CA coastal ranges and Wasatch of UT, and about 5000ft through the Mogollon Rim and northern AZ ranges along with the San Juans and CO Rockies where Day 1 WPC snow probabilities over 8" are moderately high (with totals over a foot likely along the higher Mogollon Rim and San Juans). Snow then shifts east of the southern Rockies Wednesday night with Day 2 WPC snow probabilities over 6" limited to the eastern San Juans and Sangre de Christos of CO/NM. ...Southern Plains through the Mid-Mississippi and Ohio Valleys... Days 1-3... A large scale winter weather event will begin Wednesday as an initial impulse comes off a deep Southwest U.S. trough, producing showers of sleet and freezing rain across the Southern Plains into the Mid-MS Valley Wednesday. Then a second, stronger wave comes late Wednesday night through Thursday night as the positively-tilted trough ejects east across the southern Plains before turning northeast and moving over the Midwest. This trough will ride an impressive SWly subtropical jet streak that will arc from the Desert Southwest all the way across the country into New England. Ample moist advection from the Pacific (by way of Mexico) and from the Gulf of Mexico will overrun the Arctic cold front currently pushing south down the far southern Plains and the Mid-South. The overlap of this moisture and deep layer ascent above the cold surface air will lead to widespread and prolonged wintry mix of freezing rain and sleet across the southern Plains/Mid-South, and Ohio Valley. Day 1.5 WPC probabilities for over 0.25" ice are moderate across southeast OK through northern AR to far southeast MO with Day 2.5 ice probabilities over 0.25" 20 to 30 percent over central OH. As the surface low develops and moves from the TN to eastern OH Valleys, a decent comma head develops allowing snow to expand over much of the Midwest Thursday night. Day 2.5 WPC snow probabilities for over 4" are 30 to 60 percent from eastern IA through southern MI with 40% probabilities for 6" over Chicago where enhancement from flow off southern Lake Michigan should enhance totals. ...Mid-Atlantic to New England... Day 3... Southwesterly flow aloft with an embedded shortwave trough quickly lifts through the Ohio Valley into the Northeast late Thursday into Friday. 250 mb coupled jet streak intensifies Thursday night and the associated surface low begins to deepen as it tracks through the Ohio Valley toward the Northeast. Meanwhile, strong high pressure over Ontario/Quebec will funnel much colder air through the region with cold air damming against the Appalachians. The storm system will bring a surge of higher moisture northward with the latest NAEFS showing PW anomalies reaching +2 to +3 sigma by Friday. With upwards of 1" to locally 1.5" liquid equivalent to work with, a significant snow and icing event appears increasingly likely for portions of the region Friday. The combination of the deeper frontogenesis, higher moisture in place, and sufficiently cold air will likely bring widespread 6"+ of snow to much of central/eastern NY, northern PA through much of New England. The southern periphery of the snow axis is a bit more uncertain depending on the exact surface low track and the warm nose nudging northward to or through the I-95 corridor possibly. However, the latest WPC probabilities are very high for 6" or more with even a moderate to locally high signal for 12" across the terrain/elevation areas of eastern NY into VT/NH. To the south, the cold air damming supports potentially significant ice amounts, particularly for the Laurel Highlands area where the latest probabilities of exceeding 0.25" are now up to 50 percent. Elsewhere, a stripe of around 0.10" appears most likely. Jackson/Taylor Key Messages for Feb 23-25 Winter Storm from Southern Plains through the Northeast: - A significant winter storm will bring a variety of winter hazards to the Southern Plains Wednesday and Thursday, Ohio Valley on Wednesday night through Thursday night, and the Northeast Thursday night into Friday night. - Damaging ice accumulations across the Ozarks up to 0.50†leading to power outages and tree damage are possible. This is within a swath of notable freezing rain and sleet expected from North Texas through the Mid-Mississippi Valley. - As the system moves to the Northeast Thursday night, heavy snow is increasingly likely. Widespread amounts greater than 6†are likely. - Another area of freezing rain is likely from the eastern Ohio Valley through the central Appalachians. Some significant ice accumulations are possible across south-central Pennsylvania and western Maryland. - Prepare now for this major winter storm. Widespread hazardous travel and damage to the power infrastructure are expected.