Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 336 AM EDT Sun Aug 18 2024 Valid 12Z Sun Aug 18 2024 - 12Z Tue Aug 20 2024 ....There is a Slight Risk of excessive rainfall over parts of the Mid-Atlantic on Sunday... ...There is a Slight Risk of severe thunderstorms over parts of the Mid-Atlantic to Southeast/Lower Mississippi Valley on Sunday... ...There are Excessive Heat Warnings and Heat Advisories over parts of the Southern Plains and Lower Mississippi Valley... A front extending from the Lower Great Lakes/Ohio Valley across the Tennessee/Lower Mississippi Valleys and then to the Central High Plains will move off most of the Eastern Seaboard Atlantic while lingering over the Southeast and southward off most of the Gulf Coast and then across parts of the Southern Plains by Tuesday. The boundary will produce showers and severe thunderstorms from the Mid-Atlantic, Southeast, and Gulf Coast States. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the Mid-Atlantic to Southeast/Lower Mississippi Valley through Monday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. Also, the showers and thunderstorms produced by the boundary will create heavy rain over parts of the northern Mid-Atlantic. Therefore, through Monday morning, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the northern Mid-Atlantic. 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. Additionally, an upper-level low just off the Northwest Coast will produce rain, with maybe an embedded thunderstorm over parts of the Pacific Northwest on Sunday. Furthermore, upper-level energy moving over the top of an upper-level ridge over the Central Plains will produce showers and thunderstorms over parts of the Central/Southern Plains on Sunday. Moreover, monsoonal moisture and daytime heating will create showers and thunderstorms over parts of the Southwest, Eastern Great Basin, and Northern/Central Rockies from late afternoon into late evening on Sunday and Monday. On Monday, showers and thunderstorms will develop over parts of the Northeast, Mid-Atlantic, and Southeast. While, upper-level energy will trigger showers and thunderstorms over parts of the Central/Southern Plains and Lower Mississippi Valley. Further, disorganized upper-level energy over the Northern Rockies into the Northern Plains will produce showers and thunderstorms over the region. Meanwhile, upper-level ridging over parts of the Southern Plains and Lower Mississippi Valley will produce high temperatures in the low-100s with dew points in the low to mid-70s, which have prompted Excessive Heat Warnings and Heat Advisories over parts of the Southern Plains and Lower Mississippi Valley. The sweltering summer heat will continue over the south as the prolonged stretch of high temperatures in the triple digits will focus on portions of the Southern Plains and Gulf Coast through Tuesday. Low temperatures in the low-80s/upper-70s are also forecast along the Gulf Coast, providing little relief from the heat overnight. Moreover, the combination of summer heat and high humidity will support daily maximum heat indices near 110F. Therefore, people spending more time or effort outdoors or in a building without cooling are at an increased risk of heat-related illness. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php