EF0 tornado, (Cod)Yellowstone Apt, Wyoming, June 12, 2017

1. EF065 to 85 mphthis tornado

   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. 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

EF0

Date

June 12, 2017

Touchdown

5:50 PM MDT (23:50 UTC)

Lifted

5:52 PM MDT (23:52 UTC)

On the ground

2 minutes

Path length

0.7 miles (1.1 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

County

Park County

Touchdown point

44.420, -108.910

Lift-off point

44.430, -108.910

Record number

1706121750-01

A combination of an abnormally strong upper level low, strong jet dynamics and an approaching cold front produced one of the biggest severe weather outbreaks across western and central Wyoming in many years. A total of 4 tornadoes were confirmed, including an EF2 tornado which was the strongest tornado that occurred in the NWS Riverton county warning area since 2001 which completely destroyed a trailer and threw it's base over 200 yards. There were also multiple reports of large hail, especially in Johnson County where hail up to tennis ball size was reported. In the dry slot across central and southern Wyoming, strong mid level winds mixed to the surface. The strongest winds were in the Lander foothills where wind gusts up to 76 mph occurred. Many trees were uprooted with some damage to outbuildings. Wind gusts 58 mph or over were also reported in Sweetwater County.

The public reported a tornado that briefly touched down several times in the Oregon Basin southeast of Cody. The tornado remained over open country and caused no damage.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down. One was issued for the county at another hour that day.

The county was under a severe thunderstorm watch, issued at 20:47 UTC and running to 03:29 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 0.02 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.

The Riverton/Lander radar (KRIW), 155 km away, was scanning. The volume nearest the touchdown began at 23:49 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 2017 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

20 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.