US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 416 PM EDT Mon May 04 2020 Valid Thursday May 07 2020 - Monday May 11 2020 Hazards: - Heavy rain across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Thu-Fri, May 7-May 8. - Heavy rain across portions of the Southern Plains, Fri-Sat, May 8-May 9. - Heavy rain across portions of the Southeast, Sun-Mon, May 10-May 11. - Flooding possible across portions of the Central Plains and the Southern Plains. - Flooding occurring or imminent across portions of the Southeast, the Middle Mississippi Valley, the Lower Mississippi Valley, the Great Lakes, and the Northern Plains. - Much above normal temperatures across portions of the Pacific Northwest, the Northern Rockies, and the Northern Great Basin, Fri-Mon, May 8-May 11. - Much above normal temperatures across portions of California, the Central Great Basin, the Pacific Northwest, the Northern Great Basin, and the Southwest, Thu-Mon, May 7-May 11. - Much above normal temperatures across portions of the Southern Rockies, the Southern Plains, the Southwest, the Central Great Basin, and the Central Rockies, Thu, May 7. - Much below normal temperatures across portions of the Central Plains, the Mid-Atlantic, the Lower Mississippi Valley, the Central Appalachians, the Northern Plains, the Tennessee Valley, the Middle Mississippi Valley, the Northeast, the Southern Appalachians, the Upper Mississippi Valley, the Southeast, the Great Lakes, and the Ohio Valley, Fri-Mon, May 8-May 11. - Heavy precipitation across portions of mainland Alaska, Thu-Fri, May 7-May 8. - Heavy rain across portions of mainland Alaska and the Aleutians, Fri-Sat, May 8-May 9. - Much above normal temperatures across portions of the Alaska Panhandle and mainland Alaska, Fri-Mon, May 8-May 11. - Much above normal temperatures across portions of mainland Alaska, Thu-Mon, May 7-May 11. Detailed Summary: The medium range period (Thurs, May 7 - Mon, May 11) features a highly amplified jet stream pattern across North America. A dome of high pressure in the Southwest will team up with a cresting upper level ridge extending as far north as the Arctic Circle. In addition, a potent storm system off the coast of Newfoundland and Labrador is forecast to cause a cyclonic wave break in the northwest Atlantic, forcing a blocking ridge to form over southern Greenland and over the Davis Strait. These two areas of ridging will work together to induce an intense upper trough over the eastern U.S. Mother's Day weekend and may persist into early next week. The resulting temperature regimes from this pattern in early-mid May is highlighted by summer-like conditions over the western third of the country and chilly temperatures along and east of the Mississippi River. Temperatures can reach excessively hot levels in the Southwest, California, and the Great Basin. Parts of the Desert Southwest will easily reach triple digits for highs on Thursday with overnight lows Mother's Day weekend also expected to hover between 10 to 20 degrees above normal. As the ridge build across the Northwest this weekend, much above normal temperatures will overtake the region with widespread 80s and even some 90s for highs possible. West Texas and much of New Mexico starts the period hot on Thursday, but a strong cold front cools off these areas by Friday. Speaking of "cools off", the eastern U.S. braces for temperatures that feel more like March rather than May this weekend. The coolest temperature anomalies will be spread across the Great Lakes, Ohio Valley, Mid-Atlantic, and Northeast regions. Morning lows this weekend could dip near or below freezing. In fact as a shortwave trough (guidance shows to be between -3 and -4 standard deviations from normal) passes through the Northeast Saturday, there could be a storm system forming off the coast of New England that leads to accumulating snow over northern Appalachians. Given the time of year and spread in model guidance solutions, no area for heavy snow or precipitation is shown at this time but could be added should confidence grow in the potential for heavier totals. Even if the storm does not take shape, temperatures aloft do support some upslope snowfall and scattered rain/snow showers in the northern and central Appalachians this weekend. Precipitation on average should favor drier than normal across much of the Lower 48. However, there are a few areas of note that could receive heavy rainfall. The first is from the Southern Plains to the Lower Mississippi Valley. A disturbance over the Northern Rockies Thursday morning is forecast to track into the south-central Plains where it will tap into Gulf moisture and ignite heavy showers and storms late Thursday into Friday night. Some of these storms could be severe with the potential for flash flooding too. The threat for heavy rainfall pushes south into South Texas Friday and into Saturday as a cold front approaches the region. By Sunday and into Monday, the front may stall near Florida with the chance for heavy rain and thunderstorms over the southern half of the state. Over Alaska, a low pressure system in the Gulf of Alaska is likely to cause heavy precipitation rates over portions of the Kenai Peninsula, Kodiak Island, and western shore of Cook Inlet Thursday and into Friday. Precipitation totals could exceed 4 inches with heavy snow expected in the higher elevations. Wind gusts could also be gale force along the south-central coast. Further west, a deep upper trough may tap into moisture from the subtropics and funnel it across the Aleutians. Heavy rain and gusty winds are possible there Friday and into Saturday. Last but not least, the strengthening ridge across western North America will extend into northern Alaska. The result is a dry and very mild pattern with much of the mainland and the Panhandle experiencing much above normal temperatures. Mullinax