Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 350 PM EDT Thu Jul 20 2017 Valid 00Z Fri Jul 21 2017 - 00Z Sun Jul 23 2017 ...A slight risk of severe storms for the Lower Great Lakes/Ohio Valley and the Northern High Plains through Sunday morning... ...Heavy rain likely over parts of the Upper/Middle Mississippi Valley into the Western Ohio Valley on Friday... ...Temperatures will average 10 degrees above average over parts of the Central Plains/Middle Mississippi Valley... ...Isolated heavy rain and flash flooding possible across the Southwest through the weekend... Conditions are setting up for an extended wet period for portions of the Upper Mississippi Valley and Great Lakes. A quasi-stationary frontal boundary will be present over the next few days spanning from the northern Mid-Atlantic/Northeast to the Northern/Central Plains. Multiple rounds of showers and thunderstorms will develop and move slowly along this boundary. The highest concentration of rainfall is forecast along a line from southeast Minnesota to northwest Indiana. This area has already had recent precipitation, and with an additional 1 to 3 inches anticipated, the risk for rapid runoff and flash flooding will increase. A moderate risk for excessive rainfall has been issued by WPC. Additionally, SPC has highlighted an area having a slight for severe thunderstorms to develop from the eastern Dakotas to western Ohio on Friday... and expanding northward into the Upper Great Lakes and eastward to the northern Mid-Atlantic by Saturday. Please refer the convective outlooks from SPC for more information on the severe risk. Monsoonal moisture, daytime heating and upper-level energy will continue to trigger showers and thunderstorms over parts of the Southwest/Great Basin eastward to the Central/Southern Rockies through the weekend. Higher rainfall rates will remain possible for much of the Southwest and Southern/Central Rockies, which will increase the risk for flash flooding. Slight risks for excessive rainfall will persist over much of this region through Saturday night. Moisture rich air over the Southern Mid-Atlantic/Southeast Coast and across the Gulf Coast states will interact with daytime heating and upper-level impulses to produce showers and thunderstorms. Coverage will increase during the late afternoon and evening hours. Elsewhere, onshore flow off the Pacific will aid in producing rain over parts of the Pacific Northwest through late Friday. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php