Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 348 AM EDT Thu Aug 20 2015 Valid 12Z Thu Aug 20 2015 - 12Z Sat Aug 22 2015 ...Heavy rain possible over parts of the Northern Appalachians/Northern Mid-Atlantic... ...Heavy rain possible over the southern tip of Texas... A slow moving cold front extending from the Lower Great Lakes to Western Gulf Coast will advance eastward to the Northeast/Mid-Atlantic Coast then westward to the interior Central/Eastern Gulf Coast by Friday evening. The boundary will produce showers and thunderstorms along and ahead of the front from the Lower Great Lakes to the Western Gulf Coast that will move to the East Coast by Thursday evening, remaining through Friday evening. Weak upper-level energy moving eastward out of the Central Rockies to the Central Plains on Friday will intersect return moisture from the Gulf of Mexico producing showers and thunderstorms over parts of the Southern Plains into the Lower Mississippi Valley by Friday morning, extending into parts of the Central Plains by Friday evening. Meanwhile, a front moving southeastward out of Western Canada will move into the Northern High Plains westward to the Northern Intermountain Region on Friday. The boundary will trigger showers and thunderstorms over the region Friday afternoon into evening. In addition, monsoonal moisture and day time heating will aid in developing showers and thunderstorms over parts of the Southwest/Southern Rockies during the afternoon and evening on Thursday into Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php