Deep moisture returned to the lower mid-Atlantic region during the period August 12th - 15th, with precipitable water values ranging from 1.6 to 1.9 inches each day.  A frontal boundary stalled near the Interstate 64 corridor provided a trigger for convection, supported aloft by passing upper level disturbances. Strong daytime heating contributed to deep instability, resulting in thunderstorms with high rainfall rates.  Light winds aloft resulted in mean wind speeds generally 10 knots or less, indicating slow cell movement.

Heavy Rain in TAZEWELL, VIRGINIA
From 12-AUG-20 13:00:00 to 12-AUG-20 14:00:00 (EST-5)
Location: TAZEWELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A home weather station recorded nearly 2.1 inches of rain within a 1-hour period.  This was a 25-year average return interval per NOAA Atlas 14 point frequency estimates.

Heavy Rain in TAZEWELL, VIRGINIA
From 12-AUG-20 14:00:00 to 12-AUG-20 15:00:00 (EST-5)
Location: CLAYPOOL HILL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A home mesonet station recorded 1.42 inches of rain in an hour.  About 1.3 inches fell within a 30 minute period, which equates to between a 10- and 25-year rainfall event per NOAA Atlas 14 point precipitation estimates.

Heavy Rain in FLOYD, VIRGINIA
From 12-AUG-20 07:00:00 to 14-AUG-20 07:00:00 (EST-5)
Location: COPPER HILL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

The Cooperative Weather Observer in Copper Hill, VA recorded a 2-day rainfall total of 6.46 inches from thunderstorms that occurred on the afternoons/evenings of the 12th (3.27) and the 13th (3.19).  This total is the 5th highest 2-day total to occur at this station anytime during the month of August, and the 20th highest 2-day total all-time.  Records for this station date back to April 1940.  The rainfall total of 6.46 inches represents between and 10- and 25-year rainfall event per NOAA Atlas 14 point frequency estimates.

Flood in PULASKI, VIRGINIA
From 15-AUG-20 18:03:00 to 15-AUG-20 20:30:00 (EST-5)
Location: PULASKI
Flood cause: Heavy Rain
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Peak Creek was observed overflowing its banks, with flood waters several inches deep entering buildings across portions of downtown Pulaski. Several downtown roads were closed in the area, including a portion of U.S. Highway 11 and VA Highway 99.

Debris Flow in WYTHE, VIRGINIA
From 15-AUG-20 15:45:00 to 15-AUG-20 17:00:00 (EST-5)
Location: PORTERS XRDS
Flood cause: Heavy Rain
Property damage: 8.00K
Crop damage: 0.00K
Reported by: 911 Call Center

The Wythe County 911 Operations Center reported multiple debris flows taking place along VA Highway 94 in and around the community of Ivanhoe.  Multiple rounds of thunderstorm activity, both on the 15th and in the days prior, resulted in saturated soil conditions.  The multiple rounds on the afternoon of the 15th reached up to 1.5 times the 6-hour flash flood guidance, roughly a 5-year rainfall event per FLASH estimates.

Flood in GRAYSON, VIRGINIA
From 15-AUG-20 15:15:00 to 15-AUG-20 17:15:00 (EST-5)
Location: FRIES
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A partially blocked culvert caused Dalton Creek to rise out of its banks near the Fries School, flooding the parking lot up to the building.  Radar rainfall estimates of about 1.5 inches fell within the 0.54 mi^2 (USGS Stream Stats) Dalton Creek watershed, with a personal mesonet station in the town of Fries recorded 1.48 inches rainfall in a 30-minute period, roughly a 10-year rainfall event per NOAA Atlas-14 point frequency estimates.

Flash Flood in TAZEWELL, VIRGINIA
From 12-AUG-20 13:45:00 to 12-AUG-20 15:30:00 (EST-5)
Location: TAZEWELL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Slow-moving thunderstorms produced 1.5 to 2 inches of rain within about an hour across the town of Tazewell. FLASH data indicates this amount to be 1.5 to 1.7 times greater than 1-hour flash flood guidance for this area. CREST unit streamflow for this event was 550 cfs/mi^2, while the 1-hour average return interval was around a 25-year event. Runoff from this rainfall caused flooding of several roads in the vicinity of Dogwood Road and Steeles Lane.

Flash Flood in TAZEWELL, VIRGINIA
From 12-AUG-20 14:30:00 to 12-AUG-20 17:00:00 (EST-5)
Location: CLAYPOOL HILL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Slow-moving thunderstorms produced 1.5 to 2 inches of rain within about an hour in an urbanized/highly developed area within the town of Claymont Hill. FLASH data indicates this amount to be 1.5 to 1.7 times greater than 1-hour flash flood guidance for this area. CREST unit streamflow for this event was 600-650 cfs/mi^2, while the 1-hour average return interval was around a 25-year event. Runoff from this rainfall caused flooding of roads around the Claymont Hill Mall, which were closed off until the flooding receded.  Water from the area around the mall then channeled along an unnamed creek running north adjacent to Highway 460, where flooding occurred near the Bandy Auto Care Center.

Flash Flood in MONTGOMERY, VIRGINIA
From 13-AUG-20 20:07:00 to 13-AUG-20 20:30:00 (EST-5)
Location: CHRISTIANSBURG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Two to three inches of rain fell across portions of Christiansburg during a roughly 2-hour period, which was between a 5- and 10-year event per NOAA Atlas 14 point frequency estimates.  Runoff from this rainfall caused a roadside ditch running along Phlegar Street to overflow onto the road an estimated couple feet deep between 2nd and 3rd Streets.  2nd Street was also observed to be under water and impassible.  In addition, water several inches deep was observed flowing across nearby Radford Street.

Debris Flow in SMYTH, VIRGINIA
From 15-AUG-20 15:53:00 to 15-AUG-20 15:53:00 (EST-5)
Location: CHILHOWIE
Flood cause: Heavy Rain
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

A debris flow was observed along River Road near Interstate 81 in Chilhowie. A tree and other debris slid into the road off the side of a roadside hill, blocking the road.