US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 239 PM EST Fri Feb 28 2020 Valid Monday March 02 2020 - Friday March 06 2020 Hazards: - Heavy precipitation across portions of the Pacific Northwest, Thu-Fri, Mar 5-Mar 6. - Heavy rain across portions of the Southern Plains, Lower/Middle Mississippi Valley, the Tennessee Valley, the Ohio Valley, the Southern/Central Appalachians, the Southeast, and the Mid-Atlantic, Mon-Thu, Mar 2-Mar 5. - Heavy snow across portions of the Pacific Northwest and the Northern Great Basin, Mon-Fri, Mar 2-Mar 6. - Heavy snow across portions of the Northern Rockies and the Northern Great Basin, Mon-Wed, Mar 2-Mar 4. - Severe weather across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Tue, Mar 3. - Flooding occurring or imminent across portions of the Southeast, the Middle/Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon, Mar 2. - Much below normal temperatures across portions of mainland Alaska, Mon-Fri, Mar 2-Mar 6. - Much below normal temperatures across portions of mainland Alaska, Tue-Fri, Mar 3-Mar 6. Detailed Summary: The medium range period will begin on Monday with an upper-level low centered just offshore of Southern California, which will be the main player causing potentially hazardous weather throughout the period as it pivots eastward. First, some higher than normal wave heights and breezy conditions are expected through Monday near the California coast, but should mainly remain offshore. Additionally, light to modest precipitation is expected in the Southwest ahead of the low/trough. But as the trough moves into the Plains, Pacific Ocean moisture at middle to upper levels and Gulf of Mexico moisture at low levels will combine to cause the potential for widespread heavy rainfall beginning Monday and increasing Tuesday and Wednesday. Currently, the best chance for multiple inches of rain is through Arkansas and parts of the Tennessee and Ohio Valleys. Uncertainty remains regarding the axis of the heaviest precipitation as well as the extent. Some model guidance takes heavy precipitation farther south, which would cause further issues in the Southeast given how wet they have been over the past month or so. Then by Thursday, the axis of the precipitation is less certain, with some model guidance streaming moisture into the Mid-Atlantic and Northeast, which would produce snow on the backside in the interior Northeast, while the preferred models have a more east-west axis taking rain across the southern Mid-Atlantic. In general, the event looks to be mostly rain as warmer than average temperatures are likely under the ridging ahead of the trough. Though the details have yet to be resolved, the likelihood for a heavy rainfall event somewhere in the east-central U.S. is fairly high. Additionally, the pattern should be favorable for a severe weather threat. Onshore flow from the Pacific should increase into the Northwest early in the workweek. Differences in the models regarding the forcing remain, but it seems higher elevations of the Cascades and the Northern Rockies could see some heavy snow beginning Monday. In the Northern Rockies, the snow is forecast to wind down Wednesday, but another round of precipitation is expected later in the week more toward the Pacific Northwest coast and in the Cascades. In Alaska, heavy precipitation is expected to linger in the Panhandle on Monday before decreasing. Upper-level troughing will cause below normal heights to persist through the next week. This should lead to below normal temperatures for much of the mainland throughout the period, reaching southward to the Gulf of Alaska coast starting around Tuesday. Heavy rainfall is possible over Hawaii through early next week as an upper-level low over the islands will provide forcing, and ample moisture could be drawn into this low. However, there is uncertainty as to how much moisture may make it onto land, but the Big Island could be particularly threatened by heavy rain. The upper low is expected to erode by midweek, decreasing the rainfall threat. Tate