Flash Flood — Alleghany, North Carolina

2023-07-15 to 2023-07-16 · near Cherry Lane, Alleghany, North Carolina

Event narrative

Brush Creek was flooded out of its banks at several locations by as much as 7 inches of rain falling across its headwaters. This included flooding at Brush Creek Road, Scenic Valley Road and Rich Hill Road. The bridges across Brush Creek along these roads were closed until the flood waters receded. No damage was reported to the roadways.

Wider weather episode

Thunderstorms developed, with some becoming severe, as a wave of low pressure passing along the front over western North Carolina served to increase 925 mb and 850 mb winds into the 20 kt-25 kt range from the south, tapping into deep moisture over the eastern Carolinas. By 8 pm EDT, precipitable water values across northwest North Carolina had risen as high as 2.1 inches, which is around 2 standard deviations above normal for mid-July per NWS gridded climatology estimates. Instability was also observed to be extremely high, with surface-based CAPE values in the 2,500 to 3,000 J/Kg range. In Alleghany County, a thunderstorm produced over 7 inches of rain within a 6-hour period across the headwaters of Glade Creek, with prolonged rainfall rates at 3 inches per hour. MRMS FLASH CREST Unit Streamflows registered between 600 and 800 cfs per mi^2 due to this rainfall, while 3-hour QPE/FFG indicated that the rainfall was between 2.25 and 2.5 times of the 3-hour flash flood guidance.

View location on OpenStreetMap → (36.4455, -80.9958)

Source: NOAA Storm Events Database, event_id 1125352. Narrative written by the NWS forecast office that issued the report.