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Heavy Rain and Flash Flooding Concerns in California; Heavy Snow in the Sierra

An atmospheric river will bring heavy rainfall to lower elevations of California this week, and heavy snow to the Sierra Nevada mountains. Flash flooding, some of which may be locally considerable, will be a concern on the western foothills of the Sierra Nevada mountains through Tuesday. Landslides, rockfalls and mudslides are possible in the Southern California mountains. Read More >

Overview

During the afternoon of Monday, August 14th, thunderstorms developed over the northern Black Hills. They gradually merged into a powerful supercell, which moved directly over Rapid City, bringing heavy rain, large hail, and damaging winds. The hail and winds damaged vehicles, gardens, and other property, and runoff from the heavy rain caused flooding. Meanwhile, more storms developed to the southeast of this storm. As the supercell tracked southeastward, a long duration of heavy rain resulted in flash flooding in Oglala Lakota county. Around Sharps Corner, flooding along Porcupine Creek washed out roads and stranded residents and travelers. Additional thunderstorms expanded over the area during the evening. Below are several pictures we received, a radar loop depicting the storms, and a list of significant reports. 

 

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