Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Thu Aug 17 2017 Valid 00Z Fri Aug 18 2017 - 00Z Sun Aug 20 2017 ...There is a slight risk of severe thunderstorms over parts of the Great Lakes/Ohio Valley... ...There is a slight risk of severe thunderstorms over parts of the Southern High Plains... ...Heavy rain possible over parts of the Southern Plains/Lower Mississippi Valley... ...Heavy rain possible over parts of the Mid-Atlantic and Northeast... A surface low pressure will lift through the Great Lakes region and continue through southern Ontario and Quebec... with a cold front extending from the low through the Ohio/Tennessee/Mississippi Valleys and a warm front lifting through the Appalachians and Northeast. Showers and thunderstorms will develop along and ahead of the fronts over the next few days. A few of these storms will likely become strong, or severe, producing periods of higher rainfall. On Friday portions of the Mid-Atlantic and Northeast will have slight risk for flash flooding. For the Southeast, moisture rich air and daytime heating will aid in producing showers and thunderstorms over the area through Saturday. Upper-level energy crossing the Rockies will spin up a surface low pressure east of the Southern Rockies and lift as a warm front through the Southern and Central Plains. Showers and thunderstorms will focus along this frontal boundary into the weekend. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php