US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 319 PM EST Thu Feb 13 2020 Valid Sunday February 16 2020 - Thursday February 20 2020 Hazards: - Heavy precipitation across portions of the Southern Plains, Wed-Thu, Feb 19-Feb 20. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Tue-Wed, Feb 18-Feb 19. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Wed-Thu, Feb 19-Feb 20. - Heavy snow across portions of the Central Rockies, the Central Great Basin, the Northern Rockies, and the Northern Great Basin, Sun, Feb 16. - Heavy snow across portions of the Central Rockies and Central Plains, Sun-Mon, Feb 16-Feb 17. - Heavy snow across portions of the Great Lakes and the Upper Mississippi Valley, Mon, Feb 17, then across portions of the Northeast and the Great Lakes, Tue, Feb 18. - Heavy snow across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Southern Rockies, the Southern Plains, and the Southwest, Tue-Wed, Feb 18-Feb 19. - Flooding possible across portions of the Lower Mississippi Valley, the Tennessee Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southeast, the Pacific Northwest, and the Ohio Valley. - Flooding likely across portions of the Southeast, the Mid-Atlantic, the Ohio Valley, and the Tennessee Valley. - Much below normal temperatures across portions of the Northern and Central Plains, the Northern and Central Great Basin, and the Northern and Central Rockies, Mon-Thu, Feb 17-Feb 20. - Much below normal temperatures across portions of the Central and Southern Plains, the Central and Southern Rockies, the Central Great Basin, and the Southwest, Tue-Thu, Feb 18-Feb 20. - Much below normal temperatures across portions of the Northern and Central Plains, and the Middle and Upper Mississippi Valley, Tue-Wed, Feb 18-Feb 19. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Thu, Feb 18-Feb 20. - Heavy snow across portions of southern Alaska, Sun-Tue, Feb 16-Feb 18. - Much below normal temperatures across portions of mainland Alaska, Sun-Mon, Feb 16-Feb 17 and Wed-Thu, Feb 19-Feb 20. Detailed Summary: It will be a wintry scene in the Intermountain West as heavy mountain snowfall takes shape in parts of the Great Basin and Rockies. This is due to an upper-level trough tracking through the northwestern U.S. on Sunday Snow will be measured in feet in the higher elevations this weekend. As the upper-level trough advances east Sunday night, a surface low pressure system will form in the Midwest leading to a shield of wintry precipitation forming from the Upper Mississippi Valley and into the northern Great Lakes. Confidence in snow totals, especially in more western areas of Iowa and Minnesota, are less clear due to storm track and where the best vertical motion aloft is located. Confidence in precipitation type is also unclear in the central Great Lakes where a rain/snow line along with a transitioning wintry mix zone will make snowfall forecast amounts tricky 4 days out. Eventually, the storm will track into southern Ontario on Tuesday where the threat for heavy snow will shift to northern New England. Similar to parts of the central Great Lakes, central New England may have a tougher time staying all snow due to the more northwesterly storm track. Behind this storm, a dome of high pressure will usher in bitterly cold temperatures and frigid wind chills across the Rockies and portions of the Great Plains starting Monday and persisting into the second half of next week. Easterly low-level winds will lead to heavy mountain snow in parts of southern Colorado and northern New Mexico. Temperature anomalies will average 12 to 20 degrees below normal across much of these regions with the coldest anomalies possibly located in West Texas next Wednesday and Thursday. An upper-level trough in the southwestern U.S. will generate areas of precipitation across the lower Four Corners states and West Texas which may fall in the form of heavy snow or an icy wintry mix on both Wednesday and Thursday. Farther south, Gulf of Mexico moisture out ahead of a strong cold front associated with the Midwest and New England storm system will cause scattered showers and thunderstorms to develop as early as Monday night. The Mid-South may see the most active weather on Tuesday with some precipitation totals of 1 to 2 inches possible. Due to recent heavy rainfall, flash flooding is a potential concern from the Lower Mississippi Valley to the southern Appalachians on Tuesday and lingering into Wednesday. The cold front may become stalled over Texas and the Lower Mississippi Valley the second half of the week, setting the stage for potentially more heavy rainfall in these areas. Spread in model guidance precipitation totals is high due to the disagreement in the position of this frontal boundary and the timing of when the upper-level trough in the Southwest ejects eastward. Across Alaska, below to much below normal temperatures are expected the first half of the weekend in northern and central Alaska as Arctic air remains well-entrenched. There are indications that temperatures will at least temporarily moderate over the east-central and northeastern parts of the mainland some time Tuesday as a strong Pacific storm moves into the Gulf of Alaska and possibly inland over southeastern Alaska and draws milder air northward. This storm is also responsible for the potential heavy snow across the south-central/southeastern mainland (especially the Copper River Basin area) late Sunday into Tuesday before shifting southward across the entire Panhandle Tuesday into Wednesday (where both rain and snow are expected). Arctic air building in behind this system will lead to plummeting temperatures with the core of the coldest air expected over western Alaska and the eastern Aleutians. Mullinax