Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 329 AM EDT Thu Aug 18 2016 Valid 12Z Thu Aug 18 2016 - 12Z Sat Aug 20 2016 ...There is a slight risk of severe thunderstorms over parts of the Northern Plain into the Upper Mississippi Valley... ...Heavy rain possible over parts of the Upper Mississippi Valley... ...Heavy rain possible over parts of the Central Plains... Tropical moisture pooling along an old boundary extending from the Southern Plains to parts of the Southern Mid-Atlantic and upper-level energy will aid in producing showers and thunderstorms over the region through Saturday. In addition, upper-level energy over parts of the Western Ohio Valley and Northern Appalachians will produce showers and thunderstorms over parts of the Ohio Valley into the Northeast on Thursday morning into evening. Meanwhile, a front extending from the Northern Plains roughly southwestward to the Northern Rockies will move eastward to the Upper Great Lakes and southward to the Southern High Plains by Friday evening. Showers and thunderstorms will develop along and near the boundary over the Northern Plains into the Northern Rockies on Thursday morning that will move into the Upper Mississippi Valley/Upper Great Lakes while trailing roughly southwestward into the Central High Plains and into the Northern Rockies by Thursday evening. On Friday the showers and thunderstorms will move into the Great Lakes/Ohio Valley and extend westward across parts of the Middle Mississippi Valley/Central Plains into parts of the Central High Plains/Northern Rockies. Elsewhere, monsoonal moisture and daytime heating will produce showers and thunderstorms over parts of the Southwest/Eastern Great Basin and the Southern/Central Rockies during the afternoon and evening hours on Thursday and Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php