Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 346 AM EDT Fri Aug 16 2024 Valid 12Z Fri Aug 16 2024 - 12Z Sun Aug 18 2024 ...There is a Slight Risk of excessive rainfall over parts of the Tennessee Valley and Southern Appalachians on Friday... ...There is a Slight Risk of severe thunderstorms over parts of the Central/Southern Plains on Friday... ...There are Excessive Heat Warnings and Heat Advisories over parts of the Central/Southern Plains and Lower Mississippi/Tennessee Valleys... A front extending from the Upper Great Lakes/Upper Mississippi Valley across the Middle Mississippi Valley and then to the Central High Plains will move eastward to the Lower Great Lakes/Mid-Atlantic, then westward to the Southern Plains by Sunday. Showers and thunderstorms will develop along and ahead of the boundary from the Great Lakes/Ohio Valley to the Tennessee/Lower Mississippi Valleys into the Central/Southern Plains. Additionally, the front will intersect a pool of tropical moisture over the Tennessee Valley, producing heavy rain. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Tennessee Valley/Southern Appalachians through Saturday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas the most vulnerable. Furthermore, upper-level energy moving over the Central Plains will trigger showers and severe thunderstorms. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the Central/Southern Plains and adjacent areas through Saturday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a minimal threat of tornadoes. On Saturday, as the front moves eastward, showers and thunderstorms will develop over parts of the Lower Great Lakes/Eastern Ohio Valley, Central Appalachians, Tennessee Valley, and Middle/Lower Mississippi Valley. Elsewhere, monsoonal moisture and diurnal heating will produce showers and thunderstorms over parts of the Southwest, Eastern Great Basin, and Southern Rockies from late afternoon into late evening on Friday and Saturday. Moreover, upper-level energy and moisture moving over parts of the Pacific Northwest will create rain with embedded thunderstorms over parts of the Northwest on Saturday. Meanwhile, upper-level ridging over parts of the Southern Plains and Lower Mississippi Valley with high temperatures in the upper-90s to low-100s with dew points in the low to mid-70s have prompted Excessive Heat Warnings and Heat Advisories over parts of the Central/Southern Plains and Lower Mississippi/Tennessee Valleys. The sweltering summer heat will continue over the south. A prolonged stretch of high temperatures in the upper 90s and triple digits will be focused over portions of the Southern Plains and Gulf Coast through Sunday. Low temperatures around 80 degrees are also forecast along the Gulf Coast. Moreover, the combination of summer heat and high humidity will support daily maximum heat indices near 110F. People spending greater time or effort outdoors or in a building without cooling is at an increased risk of heat-related illness. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php