A severe thunderstorm developed over the central Black Hills and tracked eastward through the Rapid City area before weakening over the plains. The storm initially contained large hail over the Black Hills, then also produced strong winds as it moved through the Rapid City area. Flash flooding also occurred in the Keystone and Rapid City areas due to two to three inches of rain.

Thunderstorm Wind in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 17:57:00 to 21-JUL-18 17:57:00 (MST-7)
Location: RAPID CITY
Magnitude: 55.00 MG
Crop damage: 0.00K
Reported by: NWS Employee

Hail in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 18:09:00 to 21-JUL-18 18:09:00 (MST-7)
Location: RAPID CITY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 18:22:00 to 21-JUL-18 18:22:00 (MST-7)
Location: RAPID CITY
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 18:22:00 to 21-JUL-18 18:22:00 (MST-7)
Location: RAPID CITY
Magnitude: 61.00 EG
Crop damage: 0.00K
Reported by: NWS Employee

Wind gusts were estimated at 70 mph.

Flash Flood in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 20:00:00 to 21-JUL-18 22:00:00 (MST-7)
Location: MT RUSHMORE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Runoff from heavy rain caused flash flooding in and around Keystone. This flash flooding was exacerbated by the already saturated ground from previous rainfall and flooding four days earlier. Water covered Grizzly Gulch Road, parts of Cemetery Road, and parking lots of businesses along Iron Mountain Road. Levels on Grizzly Bear Creek and Battle Creek quickly rose several feet.

Flood in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 21:00:00 to 22-JUL-18 13:00:00 (MST-7)
Location: KEYSTONE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Runoff from heavy rain continued to cause flooding in and around Keystone. Water covered Grizzly Gulch Road, parts of Cemetery Road, and parking lots of businesses along Iron Mountain Road. Levels on Grizzly Bear Creek and Battle Creek quickly rose several feet.

Flash Flood in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 18:45:00 to 21-JUL-18 21:00:00 (MST-7)
Location: RAPID CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Street flooding occurred throughout Rapid City. Water was reported over Third Street, St. Francis Street, Meade Street, and West Main Street. Rapid Creek quickly rose and inundated lower portions of the bike path through Rapid City.

Flood in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 21:00:00 to 22-JUL-18 08:00:00 (MST-7)
Location: RAPID CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Flooding continued along Rapid Creek, especially in Rapid Valley near Green Valley Road and Reservoir Road. The river gauge near the Water Reclamation facility crested slightly above flood stage with a peak flow around 1430 cfs.

Thunderstorm Wind in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 18:10:00 to 21-JUL-18 18:25:00 (MST-7)
Location: (RAP)RAPID CITY ARPT
Magnitude: 58.00 MG
Crop damage: 0.00K
Reported by: ASOS

Hail in LAWRENCE, SOUTH DAKOTA
From 21-JUL-18 16:15:00 to 21-JUL-18 16:15:00 (MST-7)
Location: GALENA
Magnitude: 1.50 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in LAWRENCE, SOUTH DAKOTA
From 21-JUL-18 16:33:00 to 21-JUL-18 16:33:00 (MST-7)
Location: NEMO
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 17:40:00 to 21-JUL-18 17:40:00 (MST-7)
Location: SHERIDAN LAKE
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 17:45:00 to 21-JUL-18 17:45:00 (MST-7)
Location: RAPID CITY
Magnitude: 61.00 EG
Crop damage: 0.00K
Reported by: Broadcast Media

A large tree was downed by the winds.

Thunderstorm Wind in PENNINGTON, SOUTH DAKOTA
From 21-JUL-18 17:47:00 to 21-JUL-18 17:47:00 (MST-7)
Location: RAPID CITY
Magnitude: 61.00 EG
Crop damage: 0.00K
Reported by: Public

The strong winds blew down a tree and damaged a garage door.