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Early Notice was Available for Both Flash Flood Events Last Week

Flash flood events in Tennessee and Virginia – both on the same night last week – resulted in numerous water rescues, washed-out roads, evacuation orders, damaged homes, and even a search and rescue operation1.

Flash flood warnings were issued as the event unfolded. High-resolution modeling from Baron also provided more than an hour's notice ahead of the warnings that a significant event was about to occur.

The Flash Flood Setups

Both flash flood events occurred from the same large-scale weather system – a slow-moving front, and they had a lot in common. A thunderstorm complex with multiple downpours moved over mountainous terrain across a common watershed, resulting in rapid runoff into creeks and streams through a valley community. The most affected areas by these events were near the towns of Gatlinburg, TN and Pilgrims Knob, VA.

Gatlinburg, TN

Flash Flood Radar Gatlinburg TN

Radar animation on the evening of July 12, 2022 during the Gatlinburg, TN flash flood event.

Pilgrim's Knob, VA

The variables that lead to a flash flood event are always unique, and these had their differences too. The flooding in eastern Tennessee was likely exacerbated by heavy rainfall ahead of the main storm complex, possibly aided by additional lift in the atmosphere from the Smokey Mountains. The storm cells in southwestern Virginia were training (repeating) over the same areas for more than four hours.

Timeline of Modeling and Alerts

The right combination of automated alerts and expert analysis is key to mitigating or preventing weather disasters. The timeline of alerts and data below showcase the advancements that have been made in flash flood modeling by Baron Weather. These very complex weather scenarios were [simplified] into a derived 3-level risk map to pinpoint where the extreme events were likely to occur.

Eastern Tennessee Event
8:40 pm ET
9:00 pm ET
9:30 pm ET
10:00 pm ET
11:14 pm
11:16 pm ET
2:30 am ET
Rain begins to fall
Flash Flood TN rain starts

Radar snapshot shows rain beginning to fall in the higher terrain upstream of the future flood event.

1st Baron model run
Flash Flood Risk model at 9 pm ET

Baron's exclusive Flash Flood Risk model run at 9 pm ET, showing chances are "very high" just upstream from the event in next two hours.

2nd Baron model run
Flash Flood Risk 9:30 pm ET

The next run of Baron's exclusive model continues to show "very high" chances of flash flooding, inching closer to the site of the event, also valid at 10:30 pm ET.

3rd Baron model run
Flash Flood Risk 10:30 pm ET

This is three consecutive model runs in a row showing "very high" chances of flash flooding near or just upstream of the future event by 10:30 pm ET.

Flash flooding reported
Flash Flood report TN

Flash flooding was reported at Greenbrier Campground with "multiple people stranded", evacuations ongoing, and access highways closed from three feet of water over the roadway.

Flash Flood Warning
Warning icon

National Weather Service issues Flash Flood Warning for the affected area until 3:15 am, prompted by emergency management reports of flash flooding.

Rainfall totals
TN rain totals

Radar rainfall estimates over the 6-hour period were highest in the mountains just east (or upstream) of the reported flooding.

Western Virginia Event
6:40 pm ET
7:30 pm ET
8:30 pm ET
8:33 pm ET
9:30 pm ET
10:00 pm ET
1:00 am ET
Rain begins to fall
Rain starts in VA

Radar snapshot during the onset of rain in Buchannon County, VA where flash flooding would later occur after repeating rounds of thunderstorms.

1st Baron model run
Baron Model 7:30 VA

Baron's exclusive Flash Flood Risk model run at 7:30 pm ET, showing chances are "very high" near where the event occurs later in the evening.

2nd Baron model run
FFR model VA 830

The second run of Baron's exclusive Flash Flood Risk model continued to show a "very high" chance of flash flooding, now within the next hour.

Flash Flood Warning

National Weather Service issues Flash Flood Warning for the affected area until 12:30 am local time, stating that flash flooding was "ongoing or expected to begin shortly".

Flood reports
Radar snapshot VA flood reports

Multiple reports of flash flooding come in from Buchannon County, including the news over 100 homes were inundated and 40 people were unaccounted for near Pilgrim's Knob.

Flood risk continues
final model run VA

Flash flooding is ongoing, and Baron's exclusive Flash Flood Risk model continues to show it will continue for at least two more hours.

Rainfall totals
VA rain totals

More than 6 inches of rain fell in 6 hours, nearly all of it funneled into the Big Sandy River watershed via Dismal Creek near Pilgrim's Knob.

Preparing for a sudden weather emergency, such as a flash flood, requires a multi-faceted approach. Baron Weather provides superior data that cuts through the noise when critical decisions need to be made fast.

The Flash Flood Risk guidance referenced in this story is available to developers in the Baron API, or for use by emergency response personnel in the Baron Threat Net web application.

1 Crews still searching for 3 people after Virginia flooding | AP News 

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