Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 AM EDT Fri Aug 18 2017 Valid 12Z Fri Aug 18 2017 - 12Z Sun Aug 20 2017 ...Slight risks of severe thunderstorms and flash flooding for the Mid-Atlantic on Friday... ...Heavy rain and flash flooding possible over parts of the Southwest on Saturday... A surface low pressure system located over the Upper Great Lakes is expected to track northeastward into southern Canada over the next couple of days. As it moves, its associated cold front will progress eastward through the Ohio Valley and into the Northeast and Mid-Atlantic on Friday. Along and ahead of this front, widespread showers and thunderstorms will be possible for much of the eastern U.S. There is a slight risk of severe weather as well as a slight risk for excessive rainfall/flash flooding for portions of the Mid-Atlantic on Friday. Another surface low pressure system located in the Central Plains will lead to scattered showers and thunderstorms for portions of the Plains Friday and into the Mississippi Valley by Friday evening. Heavy rain and some flash flooding is possible, particularly in portions of the Southern Plains. On Saturday, an upper-level low will move into the southwestern U.S. This will lead to showers and thunderstorms for portions of the Southwest, Southern and Central Rockies, and Southern and Central High Plains on Saturday. By Saturday night, rain and thunderstorms will become more widespread. Some storms could contain heavy rain, and flash flooding is a possibility, particularly for parts of New Mexico, where there is a slight risk of flash flooding. Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php