Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 354 AM EDT Thu Jul 18 2024 Valid 12Z Thu Jul 18 2024 - 12Z Sat Jul 20 2024 ...There is a Slight Risk of severe thunderstorms over parts of the southern Mid-Atlantic on Thursday... ...There is a Slight Risk of excessive rainfall over parts of the southern Mid-Atlantic, Southern Plains/Lower Mississippi Valley, and Southern High Plains/Southern Rockies on Thursday and over the southern Mid-Atlantic and Southern Rockies on Friday... ...There are Excessive Heat Warnings/Watches and Heat Advisories over parts of the Pacific Northwest into parts of California/Southwest... A front extending from Northern New England to the Mid-Atlantic and then southwestward to the Central Gulf Coast and western Texas will move off the Northeast and Mid-Atlantic Coast by Friday. Also, the southern half of the boundary will linger near the Southeast and across the Gulf Coast States through Friday evening. The lingering boundary will produce showers and severe thunderstorms over parts of the southern Mid-Atlantic. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the southern Mid-Atlantic through Friday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a minimal threat of tornadoes. In addition, the showers and thunderstorms will create heavy rain over parts of the southern Mid-Atlantic. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the southern Mid-Atlantic through Friday 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. A Second area of heavy rain will develop along the front over parts of the Southern Plains/Lower Mississippi Valley. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Southern Plains/Lower Mississippi Valley through Friday 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. Moreover, tropical moisture and upper-level impulses will produce showers and thunderstorms over parts of the Gulf Coast to the Southeast. Further, a third area of heavy rain will develop over parts of the Southern High Plains/Southern Rockies. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Southern High Plains/Southern Rockies through Friday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, low-lying areas, and burn scars the most vulnerable. In addition, moisture over the Southwest and daytime heating will produce showers and thunderstorms over parts of the Great Basin and Southwest from the late afternoon into late evening. Additionally, on Thursday, upper-level impulses going over an upper-level ridge over the Northern Rockies/Northern High Plains and moisture will produce scattered showers and thunderstorms over parts of the Northern/Central Rockies. On Friday, the tropical moisture and nearby boundary will produce showers and thunderstorms over the Central Gulf Coast to the Southeast and southern Mid-Atlantic. Some showers and thunderstorms will create heavy rain over parts of the southern Mid-Atlantic. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the southern Mid-Atlantic from Friday 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, monsoonal moisture and daytime heating will aid in producing showers and thunderstorms over parts of the Southwest, Great Basin, and Central/Southern Rockies from the late afternoon into late evening. An area of showers and thunderstorms will create heavy rain over parts of the Southern Rockies/High Plains. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Southern Rockies/Southern High Plains from Friday through Saturday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, low-lying areas, and burn scars the most vulnerable. Moreover, the upper-level energy moving out of the Northern Rockies into the Northern/Central Plains will produce showers and strong to severe thunderstorms with areas of heavy rain. Therefore, the SPC has issued a Marginal Risk (level 1/5) of severe thunderstorms over parts of the Northern/Central High Plains from Friday through Saturday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a minimal threat of tornadoes. Additionally, the WPC has issued a Marginal Risk (level 1/4) of excessive rainfall over parts of the Northern/Central Plains from Friday through Saturday morning. The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff with heavy rain. Meanwhile, upper-level ridging will build over the Northern Rockies to the Southwest, spawning Excessive Heat Warnings/Watches and Heat Advisories over parts of the Pacific Northwest from Thursday into Saturday. Moreover, the upper-level ridge has prompted Excessive Heat Watches and Heat Advisories over parts of California and the Southwest. The ridging will create widespread high temperatures in the 90s to 100s followed by little overnight relief, with lows in the upper 60s to 70s representing a 20-35 degree departure from average for many areas. The multi-day nature of this event will create dangerous conditions, particularly for people who are especially vulnerable to the effects of heat, such as young children, older adults, people with chronic medical conditions, and pregnant women. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php