Flash Flood — Roanoke (c), Virginia

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

Event narrative

Shafer's Crossing between 24th Street and Boulevard Street is flooded and impassible due to 2 to 3 inches of rainfall within a 90-minute period, with rainfall rates ranging from 4 to 5 inches per hour per MRMS estimates. CREST Unit Streamflow was estimated to be between 400 and 600 cfs per mile^2 for this event. No damage was reported to the road, and it was reopened to traffic after the flooding receded.

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 → (37.2807, -79.9779)

Source: NOAA Storm Events Database, event_id 1128834. Narrative written by the NWS forecast office that issued the report.