Flood — Alleghany, Virginia

2023-02-17 to 2023-02-18 · near Iron Gate, Alleghany, Virginia

Event narrative

The Cowpasture River near Clifton Forge, VA crested at 10.40 feet (Flood stage is 10 feet). This was a little over a 2-year event (50% AEP) per USGS Streamstats. The flooding was caused by between 1.5 and 2.75 inches of rain over a 24-25 hour period. No snow melt or frozen ground was involved, but the ground was moist from widespread rainfall on the 12th and 13th a few days prior. Minor lowland flooding was the only impact observed.

Wider weather episode

Prolonged rainfall over a 24- to 25-hour period ended around 8 AM EST on February 17th, which resulted in localized minor river flooding across portions of western Virginia. Unusual warmth during most of the river meant no frozen ground, snow cover or river ice in the area. However, MRMS CREST indicated that the ground was still 50 to 75 percent saturated from widespread rainfall during the 12th and 13th, just a few days prior. On the morning of the 16th, western Virginia was located on the south side of a stationary front draped near the Ohio River. Strong southwesterly windflow carried deep moisture from the Gulf of Mexico across the area, with precipitable water values (PWATs) in excess of 1.0 inch through much of the day on the 16th. PWATs would increase to around 1.2 inches by sunrise of the 17th, just as a supporting upper level trough began to push across the Appalachian chain. Rainfall rates were generally under a quarter inch per hour on the 16th, but began to increase during the overnight hours as the trough approached, in some instances exceeding an inch per hour for brief periods of time as a few thunderstorms developed, supported by Most-Unstable Layer CAPE values increasing to over 1,000 J/Kg ahead of the approaching trough. Total rainfall amounts through the event ranged from 1.75 to locally 2.50 inches, resulting in minor river flooding along the Cowpasture, Bluestone and Clinch Rivers. Other smaller tributaries experienced minor flooding as well. Multiple other rivers and creeks rose to Action stage, but remained within their banks. No flash flooding occurred. Reported impacts were limited to flooded roads with little to no damage.

View location on OpenStreetMap → (37.7856, -79.7725)

Source: NOAA Storm Events Database, event_id 1078289. Narrative written by the NWS forecast office that issued the report.