EF1 tornado, Atomic City, Idaho, May 31, 2018

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 31, 2018

Touchdown

4:00 PM MDT (22:00 UTC)

Lifted

4:30 PM MDT (22:30 UTC)

On the ground

30 minutes

Path length

12.0 miles (19.3 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

Property damage

$300

County

Bingham County

Touchdown point

43.471, -112.764

Lift-off point

43.594, -112.594

Record number

1805311600-01

Large hail, high winds, tornadoes and heavy rain all occurred in southeast Idaho on the afternoon of the 31st. Much of it occurred with one supercell which tracked northeast throughout the region.

A tornado crossed portions of the Idaho National Laboratory (INL) around East and Middle Buttes to the north and east across US 20 (including near the MFC facilities) between 400 and 430 pm MDT. Due to sparseness of population and terrain, the only damage observed was at mile marker 277 on US Highway 20 at approximately 419 pm MDT. At this point, large sections of 2 snow fences were heavily damaged Multiple steel beems were bent and twisted to varying degrees, with portions of those beems that were below the surface and moved approximately one inch. The horizontal part of these fences, make of vinyl and steel cable, were ripped apart and strewn for several yards. Large metal pieces used to hold these together were snapped and/or thrown several yards away from the fence. Other indications of tornado damage included a sign snapped off at the ground, sagebrush that was partially or completely ripped from the ground, and several small size lava rocks tossed an unknown distance. ||Based on that evidence, the tornado was assigned an EF-1 rating.

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

33 minutes of warning. NWS PIH issued a tornado warning for this county at 21:27 UTC, 33 minutes before the tornado touched down, in force until 22:01 UTC.

The county was under a severe thunderstorm watch, issued at 21:17 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 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.

The Pocatello radar (KSFX), 47 km away, was scanning. The volume nearest the touchdown began at 22:01 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 2018 tornado in IdahoEvery tornado in Idaho since 1950Warnings in force in Idaho nowThe forecast where you are

7 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.