US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 318 PM EDT Mon Apr 26 2021 Valid Thursday April 29 2021 - Monday May 03 2021 Hazards: - Heavy rain across portions of the Southern Plains, the Lower/Middle Mississippi Valley, the Tennessee Valley, the Ohio Valley, the Southern/Central Appalachians, and the Southeast, Thu, Apr 29. - Flooding possible across portions of the Central/Southern Plains and the Middle/Lower Mississippi Valley. - Flooding occurring or imminent across portions of the Lower Mississippi Valley. - Flooding likely across portions of the Lower Mississippi Valley. - Much above normal temperatures across portions of California, the Pacific Northwest, the Great Basin, the Northern Rockies, and the Southwest, Thu-Fri, Apr 29-Apr 30. - Much above normal temperatures across portions of California, the Great Basin, the Northern/Central Rockies, the Northern/Central Plains, and the Southwest, Fri-Sat, Apr 30-May 1. - Much above normal temperatures across portions of the Central Great Basin, the Central/Southern Rockies, the Southwest, the Plains, and the Upper/Middle Mississippi Valley, Sat-Sun, May 1-May 2. - Heavy precipitation across portions of the Alaska Panhandle, Thu-Fri, Apr 29-Apr 30. Detailed Summary: During the medium range period (Thursday, April 29 - Monday, May 3), a fairly progressive upper-level pattern is expected. First, an upper-level trough will move across the central and eastern U.S. and push a cold front across those areas through the end of the week. Along and ahead of the front, rain and thunderstorms are likely on Thursday, with heavy rain amounts generally from the Ark-La-Tex region northeastward into portions of the Tennessee and Ohio Valleys, the Southeast, and the Southern/Central Appalachians. Some moderate to heavy rain may continue on Friday in the Southeast, but amounts currently look like they should lessen compared to the middle of the week. Some enhanced rainfall amounts are also possible for the Northeast Thursday into Friday near the track of the surface low, but should not be too significant there. Behind this upper-level trough, an upper ridge is expected to build into the West late this workweek and move into the central U.S. this weekend. This will cause warm to hot temperatures to overspread the western half of the contiguous U.S. that are much above average for late April/early May. Temperatures are forecast to rise to over 100 degrees in the Desert Southwest, with temperatures in the 90s for portions of California late in the week and then in the Southern High Plains by the weekend. Farther north, temperatures in the 80s could stretch into the Northern Great Basin and Northern High Plains, and while higher elevations may not see temperatures quite that warm, the general warmup will be a change from the recent cool period and could cause quick melting of recent snowfall. Much of the Eastern Seaboard can also expect a warm day on Thursday, with temperatures cooling across the East by late week. Record highs and warm lows could be set or tied in the East on Thursday and in the West into the weekend. By early next week, another upper trough and low pressure/frontal system may come into the northwestern and north-central U.S., bringing chances for precipitation, gusty winds, and moderating temperatures, but model guidance does not show a consensus for heavy rain or higher elevation snow amounts at this point. These areas will continue to be monitored for future forecasts. Over Alaska, moisture across the Panhandle focused by a front and approaching low pressure system will lead to the potential for heavy precip there Thursday and Friday. Generally, coastal rain and inland snow is expected. Some model guidance indicates a ramp-up in precipitation for the Southcentral Alaska region by early next week, but confidence for remains low at this time and will depend on the track of a surface low that may move across the Gulf of Alaska. Tate