Flash Flood — Campbell, Virginia

2025-02-15 · near Posm, Campbell, Virginia

Event narrative

Little Opossum Creek was observed overflowing its banks and inundating Holcomb Path Road several inches deep. No damage was reported to the roadway, which was open to traffic after the flooding receded.

Wider weather episode

A deep upper level trough was observed exiting the southern Rockies during the morning of February 15th, with southwesterly windflow ahead of the trough allowing for a fetch of deep moisture from the western Gulf of America. This moisture pooled along a warm front situated across from Kentucky into southwest Virginia, where precipitable water values increased from 0.6 to 0.7 inches at 7 am that morning, to around 1.1 to 1.2 inches by early afternoon, which would be around 2 standard deviations above normal for mid-February. While the warm front shifted northward to the west of the Appalachians, high pressure off the Atlantic coast that was wedged against the eastern face of the Appalachians delayed the northward progress of the warm front. As such, the front remained stationary, and provided the focus for training of bands of heavy rain that fell across southwest Virginia through much of the day on February 15th. The rain fell at rates of 0.3 to 0.5 per hour beginning at around 9 am EST in the morning, which persisted for a 9-10 hour period. Rainfall totals ranged from 2 to 3 inches across southwest Virginia during this period. Soils across the area were nearly saturated from 2 rounds of widespread precipitation that fell earlier in the month. Additionally, the rain was falling over ground that was partially frozen, and covered in snow and ice from a winter storm that impacted southwest and central Virginia a few days earlier, increasing the rapid runoff potential into the creeks and rivers. In this event, CREST Unit Streamflow did not show impressive returns, while MRMS underestimated some of the precipitation totals. It was those factors combined with the high runoff potential of the rainfall that resulted in a lack of realization how quickly river levels were rising, and just how intense the flooding was becoming, even as far east as Appomattox County. CREST Hydrophobic Unit Flow proved to be a more accurate tool in this situation given the frozen ground, with returns as high as 480 cfs/m^2 across Giles County, which is where some of the most intense flooding was observed. Because MRMS was underestimating rainfall amounts, both the FLASH ARI and QPE/FFG values were also significantly underestimated. In these situation, monitoring ground-truth precipitation totals from a network of private weather stations might have prompted Flash Flood Warnings to be issued sooner.

View location on OpenStreetMap → (37.3795, -79.0987)

Source: NOAA Storm Events Database, event_id 1239905. Narrative written by the NWS forecast office that issued the report.