A line of severe thunderstorms developed over Fall River County and tracked northeast across the southern Black Hills into the west central South Dakota plains. A couple of tornadoes developed within the line across Custer County, one south of Custer and the other northeast of Custer. Trees were downed by the tornadoes and the strong straight-line winds that accompanied the line. Hail to quarter size was reported with the storms as well.

Thunderstorm Wind in FALL RIVER, SOUTH DAKOTA
From 23-MAY-21 14:41:00 to 23-MAY-21 14:41:00 (MST-7)
Location: HOT SPRINGS
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in CUSTER, SOUTH DAKOTA
From 23-MAY-21 15:00:00 to 23-MAY-21 15:00:00 (MST-7)
Location: PRINGLE
Magnitude: 52.00 EG
Crop damage: 0.00K
Reported by: Trained Spotter

Wind gusts were estimated at 60 mph.

Hail in CUSTER, SOUTH DAKOTA
From 23-MAY-21 15:02:00 to 23-MAY-21 15:02:00 (MST-7)
Location: CUSTER
Magnitude: 1.25 
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CUSTER, SOUTH DAKOTA
From 23-MAY-21 15:05:00 to 23-MAY-21 15:05:00 (MST-7)
Location: (CUT)CUSTER CO ARPT
Magnitude: 59.00 MG
Crop damage: 0.00K
Reported by: ASOS

Hail in CUSTER, SOUTH DAKOTA
From 23-MAY-21 15:08:00 to 23-MAY-21 15:08:00 (MST-7)
Location: CUSTER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Thunderstorm Wind in CUSTER, SOUTH DAKOTA
From 23-MAY-21 15:30:00 to 23-MAY-21 15:30:00 (MST-7)
Location: HERMOSA
Magnitude: 52.00 EG
Crop damage: 0.00K
Reported by: Public

Two trees were downed by the wind.

Thunderstorm Wind in MEADE, SOUTH DAKOTA
From 23-MAY-21 15:53:00 to 23-MAY-21 15:53:00 (MST-7)
Location: (RCA)ELLSWORTH AFB
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Hail in PENNINGTON, SOUTH DAKOTA
From 23-MAY-21 15:47:00 to 23-MAY-21 15:47:00 (MST-7)
Location: RAPID CITY
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in PENNINGTON, SOUTH DAKOTA
From 23-MAY-21 15:58:00 to 23-MAY-21 15:58:00 (MST-7)
Location: (RAP)RAPID CITY ARPT
Magnitude: 50.00 MG
Crop damage: 0.00K
Reported by: ASOS

Hail in PENNINGTON, SOUTH DAKOTA
From 23-MAY-21 15:58:00 to 23-MAY-21 15:58:00 (MST-7)
Location: RAPID CITY
Magnitude: 1.00 
Crop damage: 0.00K
Reported by: Public

Hail in PENNINGTON, SOUTH DAKOTA
From 23-MAY-21 15:57:00 to 23-MAY-21 15:57:00 (MST-7)
Location: RAPID CITY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Tornado in CUSTER, SOUTH DAKOTA
From 23-MAY-21 14:55:00 to 23-MAY-21 15:05:00 (MST-7)
Location: PRINGLE
Tornado F-scale: EF1
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado was reported about five miles south of Custer, just west of US Highway 385. The tornado snapped and uprooted many trees along several roads.

Tornado in CUSTER, SOUTH DAKOTA
From 23-MAY-21 15:04:00 to 23-MAY-21 15:13:00 (MST-7)
Location: CUSTER
Tornado F-scale: EF1
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado touched down just northeast of Custer and tracked to the east-northeast for over five miles. This tornado snapped several trees along Willow Creek Road.