US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 424 PM EDT Thu Mar 12 2020 Valid Sunday March 15 2020 - Thursday March 19 2020 Hazards: - Heavy precipitation for the higher elevations of southern California, Arizona, Utah, and Colorado, Mon-Thu, Mar 16-Mar 19. - Heavy snow across the higher elevations of northern California and down along the Sierra Nevada, Sun-Tue, Mar 15-Mar 17. - Heavy snow across portions of the northern Rockies, Sun, Mar 15. - Heavy rain across portions of central California, Sun-Mon, Mar 15-Mar 16. - Heavy rain across portions of the central/southern Plains eastward into the Mid-Mississippi Valley, Sun-Tue, Mar 15-Mar 17. - Heavy rain across portions of the southern Plains northeastward across the Mid-Mississippi Valley into the Ohio Valley, Wed-Thu, Mar 18-Mar 19. - Heavy rain across portions of South Dakota, Thu, Mar 19. - Flooding possible across portions of the Great Plains. - Flooding occurring or imminent across portions of the Southeast, the lower and upper Mississippi Valley, and the northern Plains. - Flooding likely across portions of the Southeast and the northern Plains. - Much below normal temperatures across portions of the interior Pacific Northwest, the northern Rockies, and into the northern Plains, Sun-Thu, Mar 15-Mar 19. - Heavy snow across portions of western Alaska, Thu, Mar 19. - High winds across western to northwestern Alaska, Wed-Thu, Mar 18-Mar 19. - High winds across portions of the Aleutians, Tue-Wed, Mar 17-Mar 18. - Much above normal temperatures across western and northern Alaska, Sun-Thu, Mar 15-Mar 19. Detailed Summary: The main story during the medium-range period will be the continual threat of heavy rain across the central portion of the country as a large and slow-moving upper low brings areas of heavy precipitation into the western U.S. A quasi stationary front will serve as a focusing mechanism for the heavy rain to redevelop while the southwesterly flow ahead of the large upper low feeds subtropical moisture from the eastern Pacific and interacts with the front. The best chance of heavy rain should be centered around areas from eastern Oklahoma to northern Arkansas each day next week. By later next Wednesday into Thursday, the threat of heavy rain should extend farther south into Texas, and then farther northeast into the Ohio Valley as a surface low pressure system is forecast to develop over the central Plains. Meanwhile, a sudden switch in the synoptic pattern over Alaska will help push a cold dome of high pressure from western Canada into the northern Rockies and the northern Plains during the weekend. Temperatures as much as 40 degrees below normal are possible with the coldest temperatures centered in northwest Montana. Although the arctic air is expected to remain confined to the northern Rockies and the northern Plains through the medium-range period, the cold upper low interacting with the arctic front will bring areas of heavy wintry precipitation slowly farther south across the northern Rockies, parts of the central Rockies, the Sierra Nevada, and even down into the higher elevations of southern California and Arizona through next Thursday. In addition, heavy rain is possible for parts of the central valley of California as the upper low deepens. Over Alaska, the recent cold spell is forecast to be rapidly placed by a warm ridge of high pressure by Sunday ahead of a strong low pressure system moving through northeastern Siberia. This will lead to a significant warm-up in temperatures across western and northern Alaska on Sunday. The axis of this upper ridge is forecast to remain nearly stationary from the Gulf of Alaska to south-central Alaska with much above normal temperatures continuing into the latter half of next week. This is when the next significant cyclone is forecast to move into the western portion of the region. It appears that gale-force winds will overspread the Aleutians with periods of rain late Tuesday into Wednesday. By Thursday, the system could spread gusty gale-force winds together with heavy snow into portions of western Alaska where blizzard conditions are possible. Kong