Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 333 AM EDT Thu Jul 29 2021 Valid 12Z Thu Jul 29 2021 - 12Z Sat Jul 31 2021 ...There is an Enhanced Risk of severe thunderstorms over parts of the Mid-Atlantic through Friday morning... ...There is a Slight Risk of excessive rainfall over parts of the Southwest, Great Basin, and the Central Rockies through Friday morning and again on Friday into Saturday morning... ...Heat Advisory over parts of the Middle/Lower Mississippi Valley and adjacent Plains as well as the Pacific Northwest; Excessive Heat Warning over parts of the same areas... A front extending from the Mid-Atlantic westward to the Northern Rockies will settle southward to the Southeast northwestward to the Central Plains and Central Rockies by Saturday. Moisture pooling along the boundary and strong dynamics will aid in producing showers and thunderstorms across the region. Therefore, the SPC has issued an Enhanced Risk of severe thunderstorms over parts of the Mid-Atlantic and a Slight Risk from the Mid-Atlantic to the Middle Mississippi Valley through Friday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. The severe thunderstorm threat will reduce slightly on Friday into Saturday over the southern Mid-Atlantic and the Middle Mississippi Valley. In addition, there is a threat of heavy rain with these thunderstorms through Saturday, too. Additionally, tropical moisture over the Gulf Coast into parts of the Southeast will produce daily showers and thunderstorms through Saturday. Meanwhile, showers and thunderstorms will continue over the Southwest, Central/Southern Rockies, and Great Basin through Saturday. The monsoonal moisture streams back into the Southwest as strong upper-level energy and other impulses passes over the region on Thursday into Saturday. Therefore, the WPC has issued a Slight Risk of excessive rainfall over the Southwest and parts of the Central Rockies on Thursday into Friday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable through Friday morning. On Friday into Saturday, the excessive rainfall threat increases with a Slight Risk threat moving into more of the Great Basin and Central Rockies. Two areas across the lower forty-eight will have heat problems; there is an Excessive Heat Warning over parts of Oregon and the Middle Mississippi/Tennessee Valleys and adjacent regions, where temperatures will be above average. Furthermore, Heat Advisories are currently in effect for portions of the Pacific Northwest/Northern California and over Middle/Lower Mississippi/Tennessee Valleys and adjacent Plains. Moreover, several regions have Air Quality Alerts due to wildfires over the Northwest into the Northern Rockies and Upper Midwest. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php