US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 307 PM EST Mon Feb 08 2021 Valid Thursday February 11 2021 - Monday February 15 2021 Hazards: - Heavy precipitation across portions of the Central Appalachians, the Mid-Atlantic, the Pacific Northwest, the Southern Appalachians, and the Northern Great Basin, Thu, Feb 11. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Thu-Fri, Feb 11-Feb 12. - Heavy snow across portions of the Central Rockies, the Central Great Basin, the Northern Rockies, and the Northern Great Basin, Thu-Fri, Feb 11-Feb 12. - Heavy snow across portions of the Central Rockies and the Central Great Basin, Fri, Feb 12. - Much below normal temperatures across portions of the Central Plains, the Great Lakes, the Lower Mississippi Valley, the Northern Plains, the Pacific Northwest, the Northern Rockies, the Middle Mississippi Valley, the Northern Great Basin, the Upper Mississippi Valley, the Southern Plains, and the Ohio Valley, Thu-Mon, Feb 11-Feb 15. - Much below normal temperatures across portions of the Central Plains, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Great Lakes, the Central Rockies, the Middle Mississippi Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Sat-Mon, Feb 13-Feb 15. - Heavy precipitation across portions of mainland Alaska, Thu, Feb 11. Detailed Summary: Cold temperatures will be the predominant story for the upcoming Day 3-7 period (Thursday, Feb 11 to Monday, Feb 15), as a deeply entrenched arctic air mass brings widespread below to much below normal temperatures to many sections of the lower 48. The greatest impacts will be over the central U.S., where temperatures will range from 25-40 degrees below normal through the entire period; this translates to an extended period of temperatures remaining below zero over the northern Plains and sections of the northern Intermountain Region. Sub-zero low temperatures will extend as far south as southern Kansas and eastward into Wisconsin/Illinois this weekend, with single digits reaching the southern Plains and into the Northeast. Any winds will exacerbate the very cold air mass, leading to dangerously low wind chills for much of this area. This arctic air mass will not entirely spare the western states as its cold air settles over the Pacific Northwest where record cold temperatures are possible late this week. A frontal boundary demarcating the southern extent of the arctic air mass will be a focus for heavy precipitation late this week as weak waves of low pressure advance along it. With relatively deep moisture in place over the Southeast, a widespread area of moderate to locally heavy rainfall will extend from the lower Mississippi Valley across the southeastern and southern Mid-Atlantic states. A challenging aspect to this forecast is the precipitation type along the northern expanse of the precipitation field. The current guidance suggests the potential for accumulating freezing rain over sections of central and southern Virginia as the arctic air mass undercuts warmer temperatures aloft. And north of that across northern Virginia/southern Maryland and Delaware could be a stripe of moderate to heavy snows, but thereā€s still a lot of uncertainty with the details at this time. Thereā€s additional uncertainty with another wave that may ride up the front. Some solutions bring a potential for another winter weather event across the northern mid-Atlantic region and southern New England. Others keep the bulk of the energy and precipitation offshore. This will be something to monitor over the next few days. Over the western U.S., a storm system is expected to move into Oregon/northern California during Thursday. This isnā€t a particularly strong system and thereā€s still some question of how far north it will track, but with arctic air in place over the Pacific Northwest, decided to include a heavy precipitation area, mainly to highlight the potential for low elevation snowfall. Moisture from this system will reach the higher terrain of western Wyoming/This system will and northern Utah during the latter part of Thursday, eventually reaching the central Rockies by early Friday. This will lead to periods of moderate to locally heavy snowfall in favored higher terrain regions. Across Alaska, the weather this period will generally be fairly settled as the predominant storm track remains south of the state. The most notable event will be focused over the Kenai Peninsula, Kodiak Island, and the northern Aleutians Thursday into Friday as a fetch of deep Pacific moisture associated with a low approaching the Gulf of Alaska will support heavy precipitation and locally windy conditions. Klein