US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 312 PM EDT Thu Apr 30 2020 Valid Sunday May 03 2020 - Thursday May 07 2020 Hazards: - Heavy rain across portions of the Upper Mississippi Valley and the Northern Plains, Sun-Tue, May 3-May 5. - Heavy rain across portions of the Lower/Middle Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Ohio Valley, Mon-Tue, May 4-May 5. - Heavy rain across portions of the Southern/Central Appalachians, the Ohio Valley, and the Tennessee Valley, Sun, May 3. - Flooding possible across portions of the Northeast, the Central Appalachians, the Middle/Upper Mississippi Valley, the Mid-Atlantic, the Great Lakes, and the Ohio Valley. - Flooding occurring or imminent across portions of the Southeast, the Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Middle Mississippi Valley, the Great Lakes, and the Northern Rockies. - Much above normal temperatures across portions of California, the Central/Northern Great Basin, the Pacific Northwest, and the Southwest, Wed-Thu, May 6-May 7. - Much above normal temperatures across portions of the Southern/Central Rockies, the Southern Plains, the Southwest, and the Central Great Basin, Sun-Thu, May 3-May 7. - Much above normal temperatures across portions of the Southern/Central Rockies, the Southern/Central Plains, and the Central Great Basin, Sun-Mon, May 3-May 4. - Much above normal temperatures across portions of the Southern Rockies and the Southern Plains, Sun-Tue, May 3-May 5. Detailed Summary: The medium range period will begin on Sunday 5/3 with quasi-zonal flow across much of the U.S., with embedded shortwaves. But an upper-level high slowly making its way over northern Mexico and then a ridge building across the West Coast should help keep heights above normal through the period over the southwestern quadrant of the nation. This will lead to much above normal temperatures over the Four Corners states and into the Central/Southern Plains through Monday, with much of Texas experiencing the heat through Tuesday. Record highs are possible for the Southern Plains for the early part of the week, with temperatures nearing 100 degrees or even exceeding it in parts of Texas. The Southwest is forecast to remain hot as well, with temperatures increasing a few degrees around midweek, and California and the Great Basin should become warmer than normal at that time too as ridging builds. Potential for heavy rainfall exists over the weekend as moisture increases along a frontal system moving through the Ohio Valley. The best chance for heavy rain is somewhere over the Ohio Valley and Central Appalachians, though differences in the latitude of the axis of heaviest rain remain. Additionally, there is some potential for moderate to locally heavy rain to the east over the Mid-Atlantic on Sunday, but rainfall amounts and position are even more uncertain there. Early next week, an upper-level trough is forecast to move across 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. Most precipitation should fall as rain, but higher elevation light snows in the Cascades and Northern Rockies are expected as temperatures cool down with the trough. Farther east, model guidance has varied in terms of how much rain will fall and where, due to differences in their handling of the shortwave trough. Currently, it seems the Northern Plains and portions of the Upper Midwest could receive potentially heavy rain early in the week. Windy conditions are also possible over the Rockies and Plains Monday, but winds should remain below hazards criteria. Downstream of the trough, another round of heavy rainfall is possible over portions of the Mississippi, Tennessee, and Ohio Valleys toward the Southern/Central Appalachians on Monday and Tuesday. Once again, confidence in the placement of the heavy rain is not too high, but moisture flowing into the vicinity of and overrunning a front is expected and could create a threat. Over Alaska, no hazards are posted. However, ice jam and snowmelt flooding are possible over portions of the mainland, though specific locations where these issues could occur are hard to pinpoint in advance. Precipitation is forecast for the Panhandle and the Gulf of Alaska coast as a low pressure system sits over the Northeast Pacific through the period, with only localized higher totals through midweek. Some model guidance shows an influx of moisture leading to potentially heavy precipitation somewhere along the coast by late next week, but low confidence remains regarding where these higher totals may occur, so will continue to monitor if a hazard area needs to be added. Temperature anomalies are not expected to be significant, though somewhat warmer than average temperatures should be persistent over the southwestern mainland. Tate