Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 413 AM EDT Thu Aug 28 2014 Valid 12Z Thu Aug 28 2014 - 12Z Sat Aug 30 2014 ...The flash flood threat is expected to shift from the Central Plains to the Upper Midwest on Thursday and into Friday... The main event to speak of this forecast period will be the heavy rain expected to shift from the Central Plains today and into the Upper Midwest by Friday. An upper level trough ejecting into the Central Plains will continue to produce an expansive area of showers and thunderstorms from the Plains to the Great Lakes. The heaviest and most organized of the convective activity should congregate ahead of the upper trough and around a surface low slowly lifting northeastward into the Upper Great Lakes. Strong thunderstorms, with embedded heavy rains, are forecast to move from the Central Plains this morning, across the Upper and Middle Mississippi Valley throughout the day, and into the Upper Midwest by tomorrow morning. As a result, WPC has highlighted a slight to moderate risk for flash flooding spanning the Central Plains to the Upper Midwest on Thursday and Friday. Meanwhile, weak tropical energy moving westward into southern Texas may bring some mainly scattered showers and thunderstorms to portions of the western Gulf Coast states, but the heaviest of the rain should remain offshore. Towards the end of the forecast period, a patch of upper level energy ahead of the main trough to the west could expand some of the precipitation into portions of the central and eastern Gulf Coast states as well. Elsewhere, a cold front dropping in from central Canada may trigger a few showers or storms across the Northern Rockies on Friday, but should remain isolated in nature since the energy and moisture associated with this system appears rather weak. Monarski Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php