Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 410 PM EDT Thu Sep 17 2015 Valid 00Z Fri Sep 18 2015 - 00Z Sun Sep 20 2015 ...There is a slight risk of severe thunderstorms over parts of the Upper/Middle Mississippi Valley through Friday morning... ...Heavy rain possible over parts of the Upper Great Lakes into the Middle Mississippi Valley through Friday morning... ...There is a slight risk of severe thunderstorms over parts of the Central Plains and Middle Mississippi Valley through Friday through Saturday morning... A slow moving cold front, draped from Ontario southwest to Colorado, will track east through the Great Lakes, Ohio Valley and south-central U.S. through by Saturday night. Moisture advecting northward from the Gulf of Mexico will pool along the boundary aiding in the development of a vast area of showers and thunderstorms. The Storm Prediction Center has identified the N Missouri/Iowa/SE Minnesota/SW Wisconsin region of having a slight risk for severe thunderstorm development through Friday morning. Heavy rain will also be possible with these storms; which will increase the threat for flash flooding. The area of highlighted risk will shift further south on Saturday as the front progresses; which includes N Oklahoma/E Kansas/NW Missouri/S Iowa/W Illinois. Multiple pulses of energy will move through the Gulf of Alaska and the Pacific Northwest; which, will produce scattered showers and thunderstorm activity from the Pacific Northwest to the Northern/Central Plains through late Friday afternoon. A complex of showers and thunderstorms will remain trapped under the upper-level ridge over Florida and the surrounding coastal areas. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php