Flash Flood — Roanoke (c), Virginia

2023-07-23 · near Roanoke, Roanoke (c), Virginia

Event narrative

The intersection of Jamison Avenue and 9th Street is flooded and impassible by several inches of flowing water caused by 3 to 4 inches of rainfall, with rates as high as 6 inches per hour. No damage was reported at the intersection, and the road was reopened to traffic after the flooding receded. MRMS FLASH CREST Unit Streamflow was estimated to be between 600 and 800 cfs per mile^2, while FLASH 1-hour ARIs indicated that rainfall amounts were as high as a 100-year event in spots around the City of Roanoke during this event.

Wider weather episode

An upper level storm system crossed the region during peak heating. The passage of this system aided in the lift needed for thunderstorm development within an already very moist and unstable atmosphere. The environment spawned scattered severe thunderstorms which produced damaging winds. In addition, storms were at times slow-moving, with winds up to 700 mb averaging around 10 knots from the southwest. Surface-based CAPEs across central Virginia varied from 1,500 to over 2,000 J/Kg during late afternoon, while precipitable water values varied from 1.2 inches across the Mountain Empire to 1.6 inches across the Southside area of Virginia. The high instability and abundant atmospheric moisture combined to produce storms with high rainfall rates, at times observed to be up to 5 inches per hour.

View location on OpenStreetMap → (37.2693, -79.9290)

Source: NOAA Storm Events Database, event_id 1128828. Narrative written by the NWS forecast office that issued the report.