US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 325 PM EST Wed Jan 12 2022 Valid Saturday January 15 2022 - Wednesday January 19 2022 Hazards: - Heavy precipitation across portions of the Mid-Atlantic and the Northeast, Sun-Mon, Jan 16-Jan 17. - Heavy rain across portions of the Southeast, the Mid-Atlantic, the Southern Appalachians, and the Tennessee Valley, Sat-Sun, Jan 15-Jan 16. - Heavy snow across portions of the Central Plains, the Middle Mississippi Valley, the Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley, Sat, Jan 15. - Heavy snow across portions of the Northeast, the Central Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Great Lakes, and the Ohio Valley, Sun-Mon, Jan 16-Jan 17. - Freezing rain across portions of the Southeast, the Mid-Atlantic, the Southern Appalachians, and the Tennessee Valley, Sat-Sun, Jan 15-Jan 16. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Pacific Northwest, and the Ohio Valley. - Flooding likely across portions of the Pacific Northwest. - Much below normal temperatures across portions of the Great Lakes, the Mid-Atlantic, the Northeast, and the Central Appalachians, Sat, Jan 15. - High significant wave heights for coastal portions of the Mid-Atlantic and the Northeast, Sun-Mon, Jan 16-Jan 17. - Heavy precipitation across portions of the Alaska Panhandle, Sat, Jan 15. Detailed Summary: A major winter storm is likely to bring hazardous wintry weather to parts of the Mid-South, Southeast, and up the East Coast this weekend and into MLK Jr. Day. Below is a synoptic overview and expected hazards from this storm system. ...Synoptic Overview... The spotlight will be fixed on the impending major winter storm tracking across the Deep South on Saturday, then across the Southeast on Sunday and eventually up the East Coast Sunday night into Monday. On Saturday, ensemble guidance is in fairly good agreement on a vigorous upper trough tracking across the Deep South. As the storm system tracks east it will tap into Gulf of Mexico moisture and direct it north into a frigid Canadian air-mass. The sub-freezing temperatures are anchored in place by a strong high pressure system in southeast Canada that acts to keep cold air locked in place from the Mid-South to the Northeast and Mid-Atlantic. At jet stream level, the deepening upper trough in the Deep South is expected to co-locate the left exit quadrant of its jet streak with the right entrance region of a more robust jet streak off the East Coast. This intrinsic setup typically gives way to rapid cyclogenesis off the Northeast coast. Frigid temperatures and abnormally warm sea surface temperatures along the East Coast also set up an increasingly baroclinic environment at the surface as well. From strong vertical ascent aloft, to a deep moisture source, a cold source region to the north, and increasingly favorable frontogentical conditions along the coast, the setup is ripe for a developing winter storm off the East Coast. ...Hazards... 1) Heavy Snow: On the northern and western side of the storm system, a swath of heavy snowfall is anticipated from parts of the Mid-South up the spine of the Appalachians and into the Northeast. The latest Winter Weather Outlook for Day 3 show shows 30-50% probabilities for greater than 0.25" of melted snow and sleet from northern Arkansas and southern Missouri on east into central Kentucky and the southern Appalachians. By Day 5 (Sunday) probabilities light up along the Appalachians of North Carolina, West Virginia, and Virginia with probabilities exceeding 70%. Heavy snow is also well agreed upon on ensemble guidance into the northern Mid-Atlantic and the interior Northeast. The southern Appalachians may receive over a foot of snow from Saturday into Sunday. North of the southern Appalachians, the heaviest totals (over a foot of snow potentially) would be along and west of I-81 from Virginia to Pennsylvania. By Monday, the storm tracks into the Northeast and the heaviest snowfall is likely to transpire in northern New England. Travel is likely to be treacherous to even impossible in these areas with gusty winds and heavy snowfall rates of 2-3" per hour causing whiteout conditions. Gusty winds as the storm intensifies off the coast could lead to power outages and tree damage. 2) Heavy Precipitation: This area from central Virginia to southern New England is likely to see a mixed bag of precipitation. Starting off as snow, some heavy snow accumulations could occur Sunday evening before the storm brings a surge of warm warm air northward and changes any lingering snowfall to a wintry mix and/or all rain. The immediate coastal areas would change over first but how quickly the snow hangs on in this area will be determined by storm track and how long Cold Air Damming (CAD) can stay in place. Regardless, precipitation forecasts have jumped in these areas over the past 24 hours anywhere from 1-1.75" of liquid precipitation. A combination of heavy snow and icy conditions could make for slick and slushy conditions on roads. 3) Freezing Rain/Sleet: A classic CAD signature is anticipated in the southern Mid-Atlantic while warm air overrunning colder sub-freezing temps at the surface allows for potentially icy conditions in parts of the Mid-South. Icing totals in the Mid-South will be lighter due to the overwhelming push of warmer air running into the air-mass with little in the way of northerly winds to help keep cold in place. Still, look for slick travel conditions in these areas on Saturday. It is a different story in northern Georgia, the western Carolinas, and south-central Virginia where strong high pressure to the north keeps a wedge of sub-freezing temps in place. Ice accumulation of 0.25-0.50" is possible in the foothills of western North Carolina and South Carolina, as well as far northern Georgia. Totals in southwest Virginia may be similar but could also see more snow than ice to start. This ice storm could cause major impacts to travel and infrastructure, most notably power outages and excessive tree damage. 4) Heavy Rain: In the warm sector, heavy rainfall is likely in parts of the Southeast. Some strong thunderstorms may also occur with localized flooding possible in some locations. 5) Coastal Flooding/High Winds: Strong onshore flow is likely to bring significant coastal impacts to the Mid-Atlantic and Northeast. Battering waves could lead to beach erosion with some storm surge potential, especially during high tide. Winds along the coast may also gust over 50 knots as the storm tracks up the coast. Flooded roads from storm surge and power outages are possible. ...Alaska... A frontal system tracking across the Gulf of Alaska ushers in a plume of moisture directed at the lower Panhandle this weekend. Locally heavy rainfall in coastal/valley areas are anticipated while heavy snow blankets the more mountains terrain. Otherwise, the North Pacific jet stream pattern feature a deep upper low west of the Aleutians and an amplifying ridge in the Gulf of Alaska. Some wet and gusty weather is possible in the Aleutians, but impacts appear to be below thresholds for the time being. Much of the mainland can expect a fairly mild pattern while colder conditions set up along the far northern coast of Alaska. Mullinax