Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 240 PM EDT Fri Aug 12 2016 Valid 00Z Sat Aug 13 2016 - 00Z Mon Aug 15 2016 ...Significant flash flood potential expected to continue for portions of the Gulf Coast and lower Mississippi valley... ...Hot and humid conditions expected to continue into the weekend for much of the East Coast... An area of low pressure that originated in the tropics will continue to drift slowly west across the lower Mississippi valley through Saturday morning before merging with a frontal system Saturday afternoon. The area of low pressure will continue to focus widespread showers and thunderstorms across the Gulf Coast and lower Mississippi valley through Saturday, with the continued threat of heavy rains over areas that have already received copious amounts of rainfall. The result will be a continued significant flash flooding potential across these areas through Saturday. After the low merges with the frontal boundary Saturday afternoon, the threat of heavy rainfall is expected to expand along the front from Saturday afternoon into Sunday, extending from the southern plains to the Northeast. The most substantial risk of flash flooding on Sunday is forecast to be across portions of the mid-Mississippi valley. Along the Eastern Seaboard, high pressure at the mid and upper-levels will expand through the weekend, keeping hot and humid conditions in place with only very isolated showers and thunderstorms during the afternoon and evening. High temperatures are forecast to be 5 to 15 degrees above average across much of the eastern U.S. on Saturday and Sunday, with many areas rising well into the 90s. These temperatures will combine with the high humidity to result in dangerous heat index values. Heat advisories as well as excessive heat watches and warnings have been issued for portions of the Mid-Atlantic and Northeast. High pressure will also remain place across the West through the weekend, keeping most areas dry with above average temperatures. Afternoon high temperatures are expected to be 5 to 15 degrees above average. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php