US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 431 PM EDT Tue Apr 28 2020 Valid Friday May 01 2020 - Tuesday May 05 2020 Hazards: - Heavy rain across portions of the Central Plains, the Lower/Middle Mississippi Valley, the Tennessee Valley, the Southern Appalachians, the Southern Plains, and the Ohio Valley, Mon-Tue, May 4-May 5. - Heavy rain across portions of the Northern Plains and the Northern Rockies, Sun-Mon, May 3-May 4. - Heavy rain across portions of the Lower/Middle Mississippi Valley, the Central/Southern Appalachians, the Tennessee Valley, and the Ohio Valley, Sat-Sun, May 2-May 3. - Heavy rain across portions of the Northeast, Fri, May 1. - Flooding possible across portions of the Middle/Upper Mississippi Valley, the Great Lakes, and the Ohio Valley. - Flooding occurring or imminent across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, the Upper Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Southeast. - Much above normal temperatures across portions of the Central/Northern Plains, the Central/Northern Great Basin, the Central/Northern Rockies, the Middle/Upper Mississippi Valley, California, and the Southwest, Fri, May 1. - Much above normal temperatures across portions of the Southern/Central Plains, the Southern/Central Rockies, the Central Great Basin, and the Southwest, Fri-Mon, May 1-May 4. - Much above normal temperatures across portions of the Southern Plains, Fri-Tue, May 1-May 5. Detailed Summary: The medium range period will begin on Friday 5/1 with a deep upper-level trough over the East, and ridging over the western and central U.S. A surface low tracking through the Northeast along with the upper low could lead to heavy rain there, continuing from the short range period. Then over the weekend, heavy rain along another frontal system is possible for areas stretching from the Middle Mississippi Valley into the Ohio Valley and Central Appalachians. Though there is a good signal for rain over an inch in a generally east-west axis, there is uncertainty with the latitude of the heaviest rain, and how far eastward the heavy rainfall reaches--some model runs have showed heavy rain eastward into the Mid-Atlantic--so will continue to monitor. Early next week, an upper-level trough is forecast to move into the Northwest and eastward into the Northern Plains by Tuesday, bringing chances for precipitation over those areas. Over the Pacific Northwest, precipitation does not seem to be anomalously high, but once precipitation spreads into the Northern High Plains, even rain amounts around an inch would be unusually high, so a heavy rain hazard area was placed there. Most precipitation should fall as rain, but higher elevation snows in the Cascades and Northern Rockies are expected as temperatures cool down with the trough. Windy conditions are also possible over the Great Basin Sunday and over the Rockies and Plains Monday, but winds look to remain below hazards criteria at this time. Downstream of the trough, another round of heavy rainfall is possible over portions of the Mississippi, Tennessee, and Ohio Valleys. Once again, confidence in the placement of the heavy rain is not too high, but moisture flowing into the vicinity of a stationary front is expected and could create a threat. The upper-level ridge will lead to much above normal temperatures over a large portion of the western and central contiguous U.S. from the short range period into Friday. Northern portions of the ridge should flatten out by the weekend, leading to temperatures closer to normal, but a persistent upper high over central Mexico should keep Texas and areas nearby above normal through early next week. Record highs are possible for the Southern High Plains several days in a row, with temperatures nearing 100 degrees or even exceeding it in southwestern Texas. Over Alaska, no hazards are posted. There is the possibility of locally heavy rain centered on the Kenai Peninsula early next week, but model guidance varies on amounts, and the threat for now looks pretty localized. Another concern is ice jam and snowmelt flooding over the mainland. Temperature anomalies are not expected to be significant. Tate