Unrated tornado, Sterling Arpt to Willard, Colorado, June 21, 2023

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 mph

   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. Unratedthis tornado

   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

Unrated

Date

June 21, 2023

Touchdown

3:35 PM MDT (21:35 UTC)

Lifted

3:46 PM MDT (21:46 UTC)

On the ground

11 minutes

Path length

1.4 miles (2.3 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

County

Logan County

Touchdown point

40.699, -103.427

Lift-off point

40.705, -103.454

Record number

2306211535-01

2 damage points were recorded along this path by NWS BOU, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 110 mph.

• Roof structure is approximately 50-years old tied to rim joist by 3-4” cooper nails.

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

Long duration severe weather event across the northeast plains, and most of the Denver metropolitan area beginning during the early afternoon hours. Scores of tornadoes occurred across Washington and Logan counties. Several rounds of hail across the Denver metro, with ping pong ball sized hail in downtown, larger hail up to 2 inches in diameter at concert in Red Rocks Amphitheatre. In all, seven patrons were hospitalized, with 83 treated on scene. A substantial number of attendees suffered welts, bruises and broken fingers trying to protect themselves. Several suffered concussions as well. A total of 33 tornadoes touched down in Washington County, with 3 reported in Logan County. There were reports of at least one home damaged west of Sterling and one commercial building collapse in Sterling. The home was damaged by one of the tornadoes.||Significant flooding and flash flooding also occurred in portions of the plains, including Elbert, Arapahoe, Adams, Logan, Washington and Morgan counties. There were likely several rural roads that flooded due to the heavy rainfall. There was a flood fatality just south of I-70 along Watkins Rd. First responders found two stranded cars swept into a field, but its occupants had either gotten out or had been rescued. The third vehicle ended up west of Watkins and 6th Ave. in what is normally a dry creek bed. South Metro���s water rescue team was then called out to do a water rescue but that operation turned into a recovery by the following morning. Due to flooding, Watkins Road was closed between Interstate 70 and Jewell Ave. Interstate 70 was also closed for several hours until water could recede from flooded underpasses. Minor flooding also occurred in portions of the Denver and the surrounding metro area. Baseball size hail was observed in Washington County. In Clear Creek County, a thunderstorm wind gusts to 68 mph was recorded.

A tornado touched down briefly in an open field. No damage was observed.

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

2 minutes of warning. NWS BOU issued a tornado warning for this county at 21:33 UTC, 2 minutes before the tornado touched down, in force until 22:00 UTC.

The county was under a tornado watch, issued at 18:36 UTC and running to 02:00 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 Enhanced Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:00 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.

Sterling (STK), 18 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Cheyenne radar (KCYS), 125 km away, was scanning. The volume nearest the touchdown began at 21:35 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 2023 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

44 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.