Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 351 AM EDT Sat Aug 22 2015 Valid 12Z Sat Aug 22 2015 - 12Z Mon Aug 24 2015 ...Severe thunderstorms and flash flooding possible across portions of the central plains and Upper Midwest... ...Below average temperatures expected for much of the central U.S. in the wake of a cold front... A deepening low pressure system and the trailing cold front will move eastward across the north central U.S. today. Scattered showers and thunderstorms are expected across the northern plains through early afternoon, but more widespread thunderstorms are forecast to develop along the cold front by late afternoon and early evening. A very unstable atmosphere will support the possibility for some thunderstorms to become severe -- and the Storm Prediction Center is forecasting a slight to enhanced risk of severe thunderstorms through tonight from portions of the central plains to the Upper Midwest. In addition to the threat of severe weather, heavy rainfall and flash flooding will be possible. Thunderstorms should weaken by Sunday morning as they move east into the Upper Great Lakes. As the cold front moves eastward, a relatively cool and fall-like air mass will move into much of the central U.S., with high temperatures 10 to 15 degrees below average in some areas. Showers and thunderstorms will be possible across the southeastern U.S. as a stationary frontal boundary weakens over the region. These showers and storms will generally be scattered, but may be more numerous today across portions of central Mississippi, Alabama, and Georgia. In the southwestern U.S., scattered showers and thunderstorms are also expected through the weekend across the Four Corners region. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php