Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 408 AM EDT Sun Aug 31 2014 Valid 12Z Sun Aug 31 2014 - 12Z Tue Sep 02 2014 ...Severe weather possible from the Central Plains to the Upper Great Lakes on Sunday and Monday... ...A slight risk for flash flooding for parts of the Lower/Middle Mississippi Valley into the Ohio Valley... ...Temperatures expected to be warmer and more humid in the East, while cooler temperatures move in across the Northwest... The biggest story this period will be a strong cold front moving eastward across the Northern Plains this morning expected to reach the Great Lakes and Middle Mississippi Valley by Monday afternoon. Ahead of this, strong southerly winds will transport warmer temperatures and plenty of moisture northward leading to a favorable set-up for heavy rain and severe weather. The main threat should begin Sunday afternoon for the Upper Midwest to the Central Plains, and continue moving eastward with the front on Monday towards the Upper Great Lakes and eventually, the Ohio Valley. Flash flooding will also be possible with some of the stronger storms, and WPC has highlighted a slight risk for parts of the Upper/Middle Mississippi Valley on Sunday, and the Middle Mississippi Valley into the Ohio Valley on Monday. Meanwhile, ahead of this system, a weak upper trough moving through aloft will continue to trigger showers and thunderstorms from the Lower Mississippi Valley to the Northeast on Sunday. While the rain should come to an end by Sunday afternoon for the southern portions of this area, it will continue into Monday for portions of the Mid-Atlantic and Northeast. In addition, with warm and muggy conditions in place, storms containing heavy rain and/or severe weather cannot be ruled out, especially across the Mid-Atlantic on Sunday. Out west, and behind the strong cold front, cooler temperatures and high pressure will prevail through Labor Day. Mainly isolated showers or storms cannot be ruled out, however, as pieces of weak energy in the flow aloft move through, especially for portions of the Northern Rockies and Plains. Scattered rain showers will also be possible across the Pacific Northwest as another shortwave moves onshore on Monday. Monarski Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php