Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 255 PM EDT Fri Apr 28 2017 Valid 00Z Sat Apr 29 2017 - 00Z Mon May 01 2017 ...Severe thunderstorms and flash flooding possible from portions of the southern plains to the Ohio valley... ...Heavy snow possible for portions of the Rockies and the adjacent High Plains... ...Above average temperatures expected for much of the eastern U.S... Several types of weather hazards are expected over the next few days, especially for southern and central portions of the U.S, as an active pattern persists. 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. Heavy snow is possible for some areas in the central and northern Rockies as well as the adjacent High Plains. As colder air spreads south on Saturday, rain is expected to change to snow across the southern Rockies as well as portions of the southern High Plains, with heavy snow once again possible for some areas. A vast area, spanning from the southern/central Plains through the Midwest/Mississippi valley and into portions of Tennessee and Ohio valleys, is forecast to have numerous showers and thunderstorms. The Storm Prediction Center has issued slight and enhanced risks for severe thunderstorms this afternoon through early Sunday morning. Refer to SPC's webpage for further details on the severe weather threat. Additionally, embedded heavy rainfall will likely impact the same region through the weekend. Areal averages of 2 to 5 inches are forecast across the central U.S. Isolated areas may exceed 7 inches. Rapid runoff of excessive rain can lead to flash flooding, as well as, river flooding. This region has already received around 400% or more of normal moisture in the last week and will be highly sensitive to additional rainfall. In general, much of the East will relatively dry as high pressure remains in place at the mid and upper levels of the atmosphere. In turn, temperatures will average 10 to 20 degrees warmer for late April for some locations. Scattered showers and thunderstorms will be possible for portions of the Mid-Atlantic region Saturday afternoon into Sunday as a cold front approaches. Campbell/Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php