Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 314 AM EDT Sat Apr 29 2017 Valid 12Z Sat Apr 29 2017 - 12Z Mon May 01 2017 ...Severe thunderstorms and flash flooding possible from portions of the southern plains to the mid-Mississippi and Ohio valleys... ...Heavy snow possible for portions of the southern/central Rockies and the adjacent High Plains... ...Above average temperatures expected for much of the eastern U.S... An active weather pattern is expected to persist across the central and eastern U.S. through the weekend and into early next week. A frontal boundary is forecast to linger from the southern plains to the mid-Mississippi and Ohio valleys as multiple waves of low pressure traverse the boundary. A deepening upper-level low moving from the Rockies into the southern plains will keep deep southerly flow in place across the central U.S., transporting abundant moisture northward for precipitation. At the surface, a low pressure system is forecast to strengthen across the southern plains today, moving northeastward to the mid-Mississippi valley by Sunday. Showers and thunderstorms are expected across a vast area spanning from the southern/central Plains through the Mississippi valley and into portions of Tennessee and Ohio valleys today and Sunday. Heavy rain may result in flash flooding for some areas, and severe thunderstorms are also possible. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Farther east, scattered showers and thunderstorms will be possible for portions of the Mid-Atlantic region Saturday afternoon into Sunday as a cold front approaches. By Monday morning the frontal system across the southern plains will begin to move into the eastern U.S., with showers and thunderstorms accompanying it. On the western side of the low pressure system, heavy snow is possible for some areas in the central and southern Rockies as well as the adjacent High Plains. By Sunday night into early Monday, as the surface low moves into the Upper Midwest, a mix of rain and snow will be possible on the northwestern side of the system across portions of the northern plains and Upper Midwest. Elsewhere, a weakening frontal system will bring rain and high elevation snow showers to the Pacific Northwest starting later Saturday. The system is forecast to spread scattered rain and snow showers into the northern and portions of the central Rockies on Sunday. Much of the East will see above average temperatures through the weekend. High temperatures will average 10 to 20 degrees above average for some locations. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php