Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 313 AM EDT Thu Sep 17 2015 Valid 12Z Thu Sep 17 2015 - 12Z Sat Sep 19 2015 ...There is a slight risk of severe thunderstorms over parts of the Upper/Middle Mississippi Valley and parts of the Upper Great Lakes... ...Heavy rain possible over parts of the Upper Great Lakes into the Middle Mississippi Valley... A slow moving front extending from the Upper Mississippi Valley to the Central Plain then westward across the Central Rockies will advance eastward to the Great Lakes/Middle Mississippi Valley to the Southern High Plains by Friday evening. Moisture from the Gulf of Mexico will pool along the boundary aiding in the development of showers and thunderstorms from the Upper/Middle Mississippi Valley into the Upper Great Lakes that will move eastward to the Great Lakes/Middle Mississippi Valley to parts of the Southern Plains by Friday evening. Meanwhile, upper-level energy over the Northwest will move eastward to the Northern/Central Plains by Friday. The energy will produce rain over the Pacific Northwest into the Northern Rockies on Thursday morning. Showers and thunderstorms will develop over parts of the Northern/Central High Plains into parts of the Central Plains by Thursday evening that will move eastward into the Northern/Central Plains by Friday morning. Elsewhere, upper-level energy over the Southeast and moisture from the Atlantic will aid in producing showers and thunderstorms over parts of the Southeast Coast and the Eastern Gulf Coast through Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php