US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 308 PM EST Thu Jan 13 2022 Valid Sunday January 16 2022 - Thursday January 20 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 and the Mid-Atlantic, Sun-Mon, Jan 16-Jan 17. - 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, and the Southern Appalachians, Sun, Jan 16. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Pacific Northwest, and the Ohio Valley. - High significant wave heights for coastal portions of the Mid-Atlantic and the Northeast, Sun-Mon, Jan 16-Jan 17. Detailed Summary: A major winter storm is forecast 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 low 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 and Southeast up the Eastern Seaboard. 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 fosters and environment suitable for rapid cyclogenesis along 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 major 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 (Sunday) shows a large swath of 50%+ probabilities of >0.25" of melted snow/sleet from the Cumberland Plateau and up the spine of the Appalachians into northern New England. Areas as far west as central and western Tennessee and as far south as far northern Mississippi and Alabama could also potentially receive heavy snowfall early Sunday morning but confidence is lower in these areas at this time. Probabilities are highest (>90% probabilities) from the Smokeys and Blue Ridge of western North Carolina on north into the central Appalachians of West Virginia, Virginia, Maryland, and south central Pennsylvania. 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 and western New York. 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: Not much has changed regarding messaging. The 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 along and west of the Mid-Atlantic and Northeast I-95 corridor before a surge of warm low level temperatures change any lingering snowfall to a wintry mix and/or all rain. The immediate coastal areas would change over to rain 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. Even still, the warm nose aloft and sub-freezing temperatures inland could briefly lead to period of sleet mixed with rain. Regardless, precipitation forecasts in this highlighted area range 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 Sunday night and into Monday. 3) Freezing Rain/Sleet: A classic CAD signature will set up shop in the southern Mid-Atlantic while warm air overrunning colder sub-freezing temps at the surface allows for icy conditions across interior portions of the Southeast. The areas most at risk for significant icing are northwest Georgia, into the western and central Carolinas, and south-central Virginia where strong high pressure to the north keeps a wedge of sub-freezing surface temperatures in place. Where low level cold holds the longest, heavy sleet accumulations are possible. Ice accumulations of 0.25-0.50" (locally exceeding 0.50") are possible in the foothills of western North Carolina and South Carolina, as well as far northwestern Georgia. Totals in southwest Virginia may be similar but could also see more snow and/or sleet than than freezing rain. This ice storm is expected to produce major impacts to travel (by ground and by air) and infrastructure with widespread power outages and excessive tree damage possible. 4) Heavy Rain: In the warm sector, heavy rainfall is likely in parts of the Southeast and along the immediate Mid-Atlantic coast. 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... The North Pacific jet stream pattern features a deep upper low west of the Aleutians and an amplifying ridge from the Gulf of Alaska to the western coast of Canada. Some wet and gusty weather is possible in the Aleutians through out the first half of the medium range, but impacts appear to be below thresholds for the time being. Ensemble guidance does hint at a storm system bringing another round of precipitation to the Panhandle and along the south-central coast, but mode; spread remains quite high. Have held off issuing any precipitation hazards for now. Much of the mainland can expect a fairly mild pattern while colder conditions set up along the far northern coast of Alaska. Mullinax