EF1 tornado, Alva, Wyoming, August 19, 2024

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

August 19, 2024

Touchdown

6:12 PM MDT (00:12 UTC)

Lifted

6:22 PM MDT (00:22 UTC)

On the ground

10 minutes

Path length

2.5 miles (4.0 km)

Path width

300 yards (274 m)

Deaths

0

Injuries

0

County

Crook County

Touchdown point

44.578, -104.497

Lift-off point

44.569, -104.448

Record number

2408191812-01

6 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 110 mph.

• Tornado tracked down the east slope and passed over and just south of the Black Tail ATV staging area and crossed Blacktail Creek
• More tree damage with evidence of circulation as the tornado crossed Blacktail Creek
• After crossing Blacktail Creek, the tornado moved up the west facing ridge just to the south of East Fork Creek. The tornado snapped numerous large pine trees with diameters near 20 inches.
• The tornado continued along the ridge just south of East Fork Road with extensive tree damage noted where road 1104 turns south

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

A thunderstorm became severe in northwest Crook County and tracked east-southeast across the county. The storm produced hail up to baseball size and wind gusts to 80 mph. The Devils Tower area sustained significant damage to trees and property. The storm also became tornadic for a brief period over the Bear Lodge Mountains, south of Alva. Many trees were either uprooted or snapped in half along the path, but no property was impacted by the tornado.

A tornado developed over the Bear Lodge Mountains, about 8 miles south of Alva, and tracked east-southeast for about two and a half miles. Numerous pine trees were either uprooted or snapped in half along its path. The estimated damage width was over a quarter mile in some areas, although some of the damage on the southern edge of the tornado was more consistent with straight line winds. No damage to property was noted. The tornado was on the ground for approximately 10 minutes with a speed of about 15 to 20 mph. The tornado was rated as an EF-1 with estimated winds up to 110 mph.

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.

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. The outlook in force was issued at 19:57 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.

Hulett (W43), 12 km from the path, in the two hours either side.

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

The Rapid City radar (KUDX), 140 km away, was scanning. The volume nearest the touchdown began at 00:13 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 2024 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

2 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.