US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 355 PM EDT Tue Mar 10 2020 Valid Friday March 13 2020 - Tuesday March 17 2020 Hazards: - Heavy precipitation across portions of California and the Southwest, Fri, Mar 13 and Mon-Tue, Mar 16-Mar 17.. - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee Valley, the Southern Plains, the Middle Mississippi Valley, California, the Southern Appalachians, the Pacific Northwest, and the Ohio Valley, Fri-Sat, Mar 13-Mar 14. - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Sun-Mon, Mar 15-Mar 16. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Southern Plains, the Middle Mississippi Valley, the Great Lakes, and the Ohio Valley, Tue, Mar 17. - Heavy snow across portions of the Pacific Northwest, the Northern Rockies, the Northern Great Basin, and the Northern Plains, Fri-Sat, Mar 13-Mar 14. - Heavy snow across portions of the Central Plains, the Central Great Basin, the Northern Plains, the Northern Rockies, the Central Rockies, California, the Northern Great Basin, and the Southwest, Sat-Mon, Mar 14-Mar 16. - Heavy snow across portions of the Central Great Basin, Sun-Tue, Mar 15-Mar 17. - Heavy snow across portions of the Southern Rockies, the Central Rockies, the Central Great Basin, the Central Plains, and the Southwest, Fri, Mar 13. - Heavy snow across portions of the Central Rockies and the Central Plains, Tue, Mar 17. - Flooding possible across portions of the Southeast. - Flooding occurring or imminent across portions of the Southeast, the Lower Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Southeast, the Upper Mississippi Valley, and the Northern Plains. - Much below normal temperatures across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Sat-Tue, Mar 14-Mar 17. - Heavy snow across portions of mainland Alaska, Fri-Sat, Mar 13-Mar 14. - High winds across portions of mainland Alaska, Fri, Mar 13. - Much above normal temperatures across portions of northern mainland Alaska, Fri-Tue, Mar 13-Mar 17. - Much above normal temperatures across portions of central mainland Alaska, Sat-Tue, Mar 14-Mar 17. - Much below normal temperatures across portions of the Alaska Panhandle and eastern mainland Alaska, Fri-Sat, Mar 13-Mar 14. Detailed Summary: The weather pattern across the continental U.S. will be highlighted by a pair of upper-level troughs digging into the Southwest and a contrasting upper-level ridge over the Gulf of Mexico. Southwest flow between these two atmospheric features will tap into a rich source of subtropical moisture and result in areas of heavy rain from the Southwest and the Southern Plains to the Lower Mississippi Valley and Mid-South. By Friday morning, the upper low will track over the Lower Colorado River Valley with the axis of heaviest precipitation on Friday focused in the south Central Great Basin, the central and Southern Rockies, and central High Plains. These areas are forecast to be cold enough to support heavy snow. Further east, an approaching cold front will trigger widespread showers and thunderstorms in the South-Central U.S. and into the Mid-South on Friday where heavy rainfall and strong thunderstorms are possible. The front is forecast to stall over southern U.S. and will lead to another round of heavy rain and thunderstorms on Saturday. As yet another upper-level trough digs south from the northeast Pacific this coming Sunday and into the first half of next week, more heavy rain is possible in Southern California with heavy snow possible in the southern mountain ranges. The heavy rain threat could return to the Mississippi and Ohio Valleys around St. Patrick's Day. Further north, a dome of cold Canadian high pressure will force temperatures to plunge across the Northern Plains and Rockies Friday and continuing into early next week. Temperature anomalies of 15 to 20 degrees below normal are possible with the coldest temperatures centered in northwest Montana. This much below normal temperature regime will set the stage for heavy mountain snow in the Northwest and the northern and central Rockies this weekend and into next Monday. Confidence is increasing that the Sierra Nevada will pick up heavy snow starting Saturday night and potentially lasting into the first half of next week. Over Alaska, an upper trough will keep frigid temperatures in the forecast over the eastern mainland and the panhandle this Friday and Saturday. As the trough heads east into northwest Canada this weekend, a strengthening ridge of high pressure will move in from the southwest leading to significantly warmer temperatures versus normal and over the last few weeks. The axis of this upper ridge is currently forecast to remain nearly stationary over the Gulf of Alaska and south-central Alaska with much above normal temperatures lasting into the start of next week. To the northwest, expect strong winds and a threat for heavy snow to develop as a potent storm system over far northeastern Russia on Friday. Mullinax