Flash Flood in Roanoke County, Virginia

Heavy rain resulted in at least 3 feet of water flooding the Shaffer's Crossing underpass area of the City of Roanoke. The occupants of at least one vehicle required swift water rescue as their car became stranded in the flood waters. After the flash flooding ended, the underpass remained flooded through much of the night. No injuries were reported, however the car sustained flood damage.

A thunderstorm developed over the City of Roanoke just before 6:45 pm EDT on August 21st, initially producing rainfall rates to nearly 5 per hour. Though the storm gradually weakened, it remained anchored over primarily the western half of the city through around 8:15 pm EDT before finally pushing away to the south. While nearly all of the city received at least 2 inches of rain, the highest totals were over the Peters Creek basin, where a 4 to 5 bullseye stretched from the Roanoke-Blacksburg Regional Airport (KROA) westward to S. Electric Road. Both the airport and a personal weather station observed rainfall totals at the 1-hour and 2-hour durations that were 500-year rainfall events per NOAA Atlas 14 Point Precipitation Frequency estimates. By 8:00 pm EDT, CREST Unit Streamflow near the airport had peaked at just over 1,600 cfs/mi^2, with much of the western half of the city observing values ranging from 550 to 950 cfs/mi^2. FLASH 1-hour Average Recurrence Intervals peaked near Electric Drive at just under a 200-year event at 7:46 pm EDT. Due to the rapid flooding of Peters Creek Road that runs alongside Peters Creek, the occupants of numerous vehicles required swift water rescues from emergency services personnel. A Flash Flood Warning with a Base tag was issued at 7:29 pm EDT for the City of Roanoke, which was upgraded to a warning with a Considerable tag at 7:52 pm EDT when reports of swift water rescues began to come in. After coordinating with the Emergency Manager of the City of Roanoke, the warning was upgraded to a Flash Flood Emergency with a Catastrophic tag at 9:02 pm EDT.