US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 342 PM EDT Thu Apr 23 2020 Valid Sunday April 26 2020 - Thursday April 30 2020 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Sun-Mon, Apr 26-Apr 27. - Heavy precipitation across portions of the Northeast, Sun, Apr 26. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Tue, Apr 28. - Heavy rain across portions of the Northeast, the Central Appalachians, the Mid-Atlantic, the Southern Appalachians, the Great Lakes, and the Ohio Valley, Wed-Thu, Apr 29-Apr 30. - Heavy rain across portions of the Mid-Atlantic, the Northeast, and the Central Appalachians, Sun, Apr 26. - Flooding possible across portions of the Northern Plains. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Northern Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, the Southeast, and the Southern Plains. - Flooding likely across portions of the Southeast and the Tennessee Valley. - Much above normal temperatures across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Northern Plains, the Southern Plains, the Northern Great Basin, the Southern Rockies, California, the Northern Rockies, the Pacific Northwest, and the Southwest, Sun-Thu, Apr 26-Apr 30. - Much below normal temperatures across portions of the Northeast, the Central Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Great Lakes, and the Ohio Valley, Sun-Mon, Apr 26-Apr 27. - High winds across portions of the Alaska Panhandle, Sun-Wed, Apr 26-Apr 29. - High winds across portions of the Aleutians, Tue-Wed, Apr 28-Apr 29. Detailed Summary: The medium-range period (Sun, Apr 26 to Thurs, Apr 30) in the West is headlined by a strong ridge of high pressure centered over the Southwest. A dome of much above normal temperatures will engulf the Desert Southwest, California, the Great Basin, and the Four Corners throughout the period. High temperatures are forecast to soar into the triple digits in portions of the Desert Southwest Sunday and continue into next week, making it the region's first heat wave of the season. By mid-week the warmest temperatures versus normal are forecast to be located over California and the Great Basin. To the north, a steady stream of Pacific moisture will be aimed at the Pacific Northwest. The heaviest round of precipitation looks to arrive Sunday evening and continue into Monday as a frontal system passes through the region. The primary precipitation type will be rain but some heavy higher elevation snowfall in the Cascades is also possible. Further east, a series of upper level troughs will rotate through the eastern half of the Lower 48. An upper level feature exiting the Rockies will track east and deepen while doing so. The storm will head for the central Appalachians late Saturday and by Sunday, a coastal low will form off the East Coast making for a wet, dreary, and gusty Sunday across the Mid-Atlantic and Northeast. The prolonged fetch of Atlantic moisture has led to model guidance keying in on an area of heavy rain over southern New England and the northern Mid-Atlantic, but there are still some discrepancies on exact placement of heaviest rainfall due to differences in storm track. To the north, the higher elevations of New England are likely to contend with periods of snow while lower elevations see rain. An area of heavy precipitation remains in place over parts of the northern Appalachians for Sunday. Additionally, the signal for yet another upper level trough ushering in more unsettled weather across the eastern half of the country mid-week is coming into focus. The threat for heavy rain and thunderstorms should develop over the Lower Mississippi Valley on Tuesday. Heavy showers and strong thunderstorms could also transpire in the Mid-South late Tuesday. There could also be an area of heavy rain across the Upper Mississippi Valley and into the Great Lakes Tuesday into Wednesday, but confidence in heavy rainfall totals and where they take place is low at this time. As the storm tracks into the Great Lakes mid-week, periods of rain will advance up the East Coast including the potential for heavy rain from the central Appalachians to the Northeast. Over Alaska, temperatures will remain cooler than normal for most of the mainland but not cold enough to trigger a much below normal temperature area. To the south, a pair of occluded storm systems will slam into the Panhandle both this weekend and the first half of the week. Plenty of precipitation is in the forecast but precipitation rates are not forecast to become excessive at this time. Should trends become wetter, there may be a need for a heavy rain or precipitation area in the future forecasts. However, high winds along the Panhandle coast are possible Sunday and potentially into Monday as well. As yet another storm system approaches mid-week, yet another period of strong winds will arrive in roughly the same area. Out west, a powerful upper low in the northwest Pacific may reach the Aleutians as early as Tuesday and generate strong winds, specifically in the western most islands. Mullinax