A severe thunderstorm developed over the higher elevations of the central Black Hills and tracked east-southeast through the foothills before dissipating over the plains. The storm produced large hail from near Sheridan Lake to Fairburn. Heavy rain also caused flash flooding in areas from Keystone to near Hermosa.

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 13:20:00 to 17-JUL-18 13:20:00 (MST-7)
Location: MYSTIC
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 14:10:00 to 17-JUL-18 14:10:00 (MST-7)
Location: HILL CITY
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 14:16:00 to 17-JUL-18 14:16:00 (MST-7)
Location: HILL CITY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Nickel sized hail covered the ground.

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 14:22:00 to 17-JUL-18 14:22:00 (MST-7)
Location: HILL CITY
Magnitude: 1.25 
Crop damage: 0.00K
Reported by: Public

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 14:25:00 to 17-JUL-18 14:25:00 (MST-7)
Location: HILL CITY
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail covered the ground.

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 14:30:00 to 17-JUL-18 14:45:00 (MST-7)
Location: HILL CITY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Hail in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 14:47:00 to 17-JUL-18 14:57:00 (MST-7)
Location: HAYWARD
Magnitude: 1.75 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail to golf ball size covered the ground.

Hail in CUSTER, SOUTH DAKOTA
From 17-JUL-18 15:29:00 to 17-JUL-18 15:29:00 (MST-7)
Location: CUSTER
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: Park/Forest Service

Quarter sized hail was reported at the Custer State Park Headquarters office.

Hail in CUSTER, SOUTH DAKOTA
From 17-JUL-18 15:50:00 to 17-JUL-18 15:50:00 (MST-7)
Location: FAIRBURN
Magnitude: 1.50 
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in CUSTER, SOUTH DAKOTA
From 17-JUL-18 16:05:00 to 17-JUL-18 16:05:00 (MST-7)
Location: FAIRBURN
Magnitude: 52.00 EG
Crop damage: 0.00K
Reported by: NWS Employee

Wind gusts were estimated at 60 mph.

Flash Flood in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 15:00:00 to 17-JUL-18 17:45:00 (MST-7)
Location: MT RUSHMORE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Runoff from heavy rain, exacerbated by hail covered roads, caused flash flooding in and around Keystone. Runoff also caused flooding around Mount Rushmore, where the walking trail was briefly inundated from water rushing down the stairs between the Grandview Terrace and the Sculpture Studio. Water covered Grizzly Gulch Road, parts of Cemetery Road, and several parking lots of businesses along Iron Mountain Road. River levels on Grizzly Bear Creek and Battle Creek quickly rose several feet.

Flood in PENNINGTON, SOUTH DAKOTA
From 17-JUL-18 17:45:00 to 18-JUL-18 08:00:00 (MST-7)
Location: MT RUSHMORE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Runoff from heavy rain, exacerbated by hail covered roads, continued to cause flooding in and around Keystone. Runoff also caused flooding around Mount Rushmore, where the walking trail was briefly inundated from water rushing down the stairs between the Grandview Terrace and the Sculpture Studio. Water covered Grizzly Gulch Road, parts of Cemetery Road, and several parking lots of businesses along Iron Mountain Road. River levels on Grizzly Bear Creek and Battle Creek quickly rose several feet.

Flood in CUSTER, SOUTH DAKOTA
From 18-JUL-18 04:00:00 to 18-JUL-18 13:00:00 (MST-7)
Location: HERMOSA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Minor flooding was observed along Battle Creek and Grace Coolidge Creek upstream of Highway 79. Several pastures and agricultural land were inundated. The river gauge on Battle Creek at Hermosa reached flood stage briefly.