Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 343 AM EDT Thu Aug 21 2014 Valid 12Z Thu Aug 21 2014 - 12Z Sat Aug 23 2014 ...Slight risk of severe thunderstorms across portions of the Middle Missouri Valley southeastward across parts of the Great Lakes and the Western Ohio Valley... ...Heavy rain possible over portions of the Ohio Valley/Central Appalachians and the Southern Mid-Atlantic... ...Heavy rain possible over portions of Northern Rockies/High Plains... A persistent boundary extending across parts of the Upper Midwest to the Ohio Valley and the Mid-Atlantic will have upper-level impulses transiting the region along with moisture rich air pooling over the area through Friday. Showers and thunderstorms will develop along and ahead of the front on Thursday into Friday. Meanwhile, an upper-level trough roughly over the Northern Rockies will have embedded disturbances moving through the trough while upslope flow will aid in producing showers and thunderstorms over parts of the Great Basin and the Northern Rockies/High Plains as well as parts of the Northern Plains through Friday. In addition, upper-level energy over Southern California/Southwest will move northeastward to the Central/Southern Rockies by Friday evening. Showers and thunderstorms will develop over parts of the Southwest and expand into parts of the Great Basin by Thursday evening. The showers and thunderstorms will move to the Southern/Central Rockies on Friday spilling over into parts of the Central Plains by Friday evening. Furthermore, general instability and ample moisture will aid in producing showers and thunderstorms over parts of Florida through Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php