US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 358 PM EDT Tue May 26 2020 Valid Friday May 29 2020 - Tuesday June 02 2020 Hazards: - Heavy rain across portions of California, the Pacific Northwest, and the Northern Great Basin, Sat, May 30. - Heavy rain across portions of the Southeast and the Mid-Atlantic, Fri, May 29. - Flooding possible across portions of the Lower Mississippi Valley, the Southern Plains, the Northern Rockies, the Middle Mississippi Valley, the Southeast, and the Great Lakes. - Flooding occurring or imminent across portions of the Northern Plains, the Southern Plains, the Northern Rockies, the Middle Mississippi Valley, the Mid-Atlantic, the Southeast, and the Great Lakes. - Flooding likely across portions of the Central Plains, the Southeast, the Middle Mississippi Valley, and the Southern Plains. - Much above normal temperatures across portions of the Central Great Basin, the Northern Rockies, California, the Northern Great Basin, the Pacific Northwest, and the Southwest, Fri-Sat, May 29-May 30. - Much above normal temperatures across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Northern Plains, the Northern Rockies, the Southern Rockies, the Northern Great Basin, and the Southwest, Fri-Tue, May 29-Jun 2. - Much above normal temperatures across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Sun-Tue, May 31-Jun 2. - Much above normal temperatures across portions of mainland Alaska, Fri-Tue, May 29-Jun 2. Detailed Summary: The medium range forecast period (May 29 - June 2) is characterized by upper level ridging over the Intermountain West and central U.S. while an upper trough approaches the West Coast. Most of the eastern U.S. can expect high pressure for much of the period with cooler northwest flow aimed at the Great Lakes and Northeast. The most commonly observed hazard is likely to be an expansive area of scorching temperatures over the Great Basin, the Rockies, and High Plains. The core of much above normal warmth will start across the western third of the CONUS with only the immediate coastline staying cooler. As the upper trough over the northeast Pacific approaches the West Coast this weekend, the dome of sizzling temperatures should spread east into the Rockies and High Plains. By the time the calendar flips over to June, the warmest temperature departures are forecast to set up over the north-central region where heat indices may surpass the century mark. Precipitation-wise, the central U.S. can anticipate an abnormally dry pattern as high pressure dominates overhead. Meanwhile, a wet start to the period is likely to occur along the East Coast as a cold front approaches from the west. A weak upper-level feature in the Deep South may trigger heavy showers and thunderstorms in the Southeast. Above normal moisture content will also be present, allowing for the chance of heavy rainfall on Friday. There is also the potential for heavy rain in the Northeast late Friday into Saturday, but excessive totals could be more widely scattered there than in the Southeast. The other area of note is the Northwest as a potent upper trough will swing up the West Coast on Saturday. Rainfall totals of 1-2" are possible over western Oregon and portions of northern California. Over Alaska, above normal temperatures are forecast to persist from the North Slope to the western mainland with a upper-level high pressure forecast to stick around into the start of June. Ice jam flooding remains a concern over the North Slope as rivers have not yet broken up, while minor snowmelt flooding is a possibility in central and southern parts of the mainland. Farther south, a North Pacific upper trough will make for a wet Friday in the eastern Aleutians, but totals likely fall just short of heavy rainfall criteria. The same can be said for the southern mainland as a storm system in the Gulf of Alaska stays just far enough south to keep precipitation totals just shy of meeting heavy rainfall/precipitation criteria. Should guidance become wetter in the coming days, it is possible to see heavy rain or precipitation areas be issued later this week. Mullinax