US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 348 PM EDT Mon Mar 09 2020 Valid Thursday March 12 2020 - Monday March 16 2020 Hazards: - Heavy precipitation across portions of Southern California, Fri, Mar 13 and Mon, Mar 16. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Southern Plains, California, the Southern Appalachians, the Pacific Northwest, and the Ohio Valley, Sat-Sun, Mar 14-Mar 15. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Plains, the Ohio Valley, and the Southwest, Thu-Fri, Mar 12-Mar 13. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Mon, Mar 16. - 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-Mon, Mar 15-Mar 16. - Heavy snow across portions of the Southern Rockies, the Central Rockies, the Central Great Basin, the Central Plains, and the Southwest, Fri, Mar 13. - Flooding possible across portions of the Southeast. - Flooding occurring or imminent across portions of the Southeast, the Lower Mississippi Valley, and the Northern Plains. - Flooding likely across portions of 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-Mon, Mar 14-Mar 16. - Heavy snow across portions of mainland Alaska, Thu-Fri, Mar 12-Mar 13. - High winds across portions of mainland Alaska, Thu-Fri, Mar 12-Mar 13. - Much above normal temperatures across portions of northern mainland Alaska, Fri-Mon, Mar 13-Mar 16. - Much above normal temperatures across portions of central mainland Alaska, Sat-Mon, Mar 14-Mar 16. - Much below normal temperatures across portions of the Alaska Panhandle and mainland Alaska, Thu-Fri, Mar 12-Mar 13. Detailed Summary: The weather pattern across the continental U.S. will be highlighted by a series 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. As the upper low tracks through the Southwest, highly anomalous atmospheric moisture will engulf the region and may lead to heavy rain and flash flooding concerns in parts of southwestern California and central Arizona this Thursday and Friday. Heavy mountain snow is also possible in the higher elevations of Southern California and in the southern Rockies on Friday. 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 early 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 Southern Plains the first half of next week. Further north, a dome of cold Canadian high pressure will force temperatures to plunge across the Northern Plains and Rockies beginning Friday and continuing through the upcoming weekend. Temperature anomalies of 15 to 20 degrees below normal are possible. This cold 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. Even the Sierra Nevada may 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 Thursday and Friday. As the trough heads east into northwest Canada this weekend, a strengthening ridge of high pressure will move in from the west leading to significantly warmer temperatures versus normal and over the last few weeks. This 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 this Thursday into Friday. Mullinax