A series of training thunderstorms produced extremely high rainfall across portions of Patrick and Carroll Counties during the predawn hours of August 28th. This resulted in areas of flash flooding, mainly in the headwaters of the Smith River and the Ararat River.
The event began with a stationary front draped near the border of Virginia and North Carolina early on the 28th as an upper level disturbance began passing across the lower Great Lakes, placing the central Appalachians in an area of lift. The disturbance triggered a southeasterly wind shift across the foothills of the Blue Ridge in southern Virginia and northern North Carolina, bringing an increase of deep moisture northeast from the Piedmont of North Carolina. Precipitable water values were estimated to|be 1.9 to 2.1 inches across Patrick and Carroll counties by 3:00 am on the 28th, while Mixed-Layer CAPE values remained around 500 J/Kg through much of the night.
Convection initiated after sunset on the 27th as a few slow-moving showers across southern Patrick County. Coverage and intensity of the slow-moving activity only increased as the evening progressed, with a band of showers and embedded storms forming along the Highway 58 corridor by midnight, that was advancing northeast toward the crest of the Blue Ridge. Deep moisture combined with orographic lift to produce extremely efficient rainfall rates that were, at times, ranging from 3 to 5 inches per hour across Patrick County into neighboring Carroll County. Doppler Radar estimated rainfall totals of nearly 11 inches of rainfall in northern Patrick County across the Smith River basin, which was confirmed by one CoCoRaHS report of 10.70 inches, as well as a Cooperative Observer report from Woolwine of 10.62 inches. The stream gage at the Smith River near Woolwine (SMWV2) rose to 11.04 feet, just above moderate flood stage due to this rainfall, however radar estimates put the highest amounts downstream of this gage. Few reports of flooding impacts were received, however it was noted that Philpott Reservoir rose 3 feet in response to the inflows from the Smith River. In western Patrick County and southeast Carroll County, 4 to 7 inches of rain fell across the entire headwaters of the Ararat River, with radar estimates of around 9 inches near the town of Ararat, VA. Flash flooding in this area resulted in several roads being destroyed or heavily damaged where they passed over flooded creeks and rivers, including the Ararat River.