EF1 tornado, Pringle to Custer, South Dakota, May 23, 2021

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF1

Date

May 23, 2021

Touchdown

4:04 PM MDT (22:04 UTC)

Lifted

4:13 PM MDT (22:13 UTC)

On the ground

9 minutes

Path length

5.9 miles (9.4 km)

Path width

10 yards (9 m)

Deaths

0

Injuries

0

County

Custer County

Touchdown point

43.780, -103.580

Lift-off point

43.810, -103.470

Record number

2105231604-01

4 damage points were recorded along this path by NWS UNR, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 104 mph.

• Prelim Start Point Custer Co Tor 1
• Prelim end point of Custer CO Tor 2
• Prelim End Point of Custer Co Tor 1
• Prelim Start Point of Custer Co Tor 2

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

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.

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.

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.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

5 minutes of warning. NWS UNR issued a tornado warning for this county at 21:59 UTC, 5 minutes before the tornado touched down, in force until 22:30 UTC.

The county was under a tornado watch, issued at 19:51 UTC and running to 00:39 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:53 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

The Rapid City radar (KUDX), 67 km away, was scanning. The volume nearest the touchdown began at 22:02 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2021 tornado in South DakotaEvery tornado in South Dakota since 1950Warnings in force in South Dakota nowThe forecast where you are

11 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.