Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 408 AM EDT Fri Aug 11 2017 Valid 12Z Fri Aug 11 2017 - 12Z Sun Aug 13 2017 ...Heavy rain possible over parts of the Southern Plains... ...Heavy rain possible over parts of the Southern Mid-Atlantic... A front extending from the Great Lakes to Middle Mississippi Valley then westward across the Southern Plains will slowly move eastward to the Northern Appalachians/Mid-Atlantic into the Southeast and westward across the Gulf Coast States into the Southern Plains by Sunday. Showers and thunderstorms will develop along and ahead of the boundary from the Great Lakes into the Middle Mississippi Valley and into parts of the Central/Southern Plains that will move eastward to the Northeast/Mid-Atlantic Coast and extend westward to the Southern Plains by Saturday evening into Sunday. In addition, moisture rich air over the Gulf Coast States/Southeast and Southern Mid-Atlantic will interact with daytime heating and upper-level jet dynamics to produce showers and thunderstorms over the Central Appalachians/Mid-Atlantic into parts of the Tennessee/Lower Mississippi Valleys on Friday afternoon and evening that will wane over parts of the Tennessee/Lower Mississippi Valleys Friday night into Saturday morning. The showers and thunderstorms will redevelop over parts of the Lower Mississippi Valley into the Southeast on Saturday. The showers and thunderstorms will continue over parts of the Mid-Atlantic into the Northeast Friday night into Saturday afternoon. Meanwhile, upper-level impulses over the Southwest and the Northern Intermountain Region/Central Rockies along with daytime heating will aid in developing showers and thunderstorms over parts of the Northern Rockies/Great Basin and the Southwest that will expand into parts of the Central/Southern Rockies by Friday evening. As some of the upper-level impulses move onto the Northern Plains, showers and thunderstorms will develop over the Northern Plains overnight Friday into Saturday evening. The showers and thunderstorms will also expand into parts of the Central Plains on Saturday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php