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.

Tornado in BINGHAM, IDAHO
From 31-MAY-18 15:00:00 to 31-MAY-18 15:30:00 (MST-7)
Location: ATOMIC CITY
Tornado F-scale: EF1
Property damage: 0.30K
Crop damage: 0.00K
Reported by: NWS Storm Survey

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.

Thunderstorm Wind in POWER, IDAHO
From 31-MAY-18 14:15:00 to 31-MAY-18 14:26:00 (MST-7)
Location: AMERICAN FALLS
Magnitude: 77.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

The Crystal RAWS measured an 89 mph wind gust.

Thunderstorm Wind in BINGHAM, IDAHO
From 31-MAY-18 15:10:00 to 31-MAY-18 15:20:00 (MST-7)
Location: ATOMIC CITY
Magnitude: 59.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWSS

The Atomic City ARL site recorded a 68 mph wind gust.

Tornado in JEFFERSON, IDAHO
From 31-MAY-18 15:31:00 to 31-MAY-18 15:36:00 (MST-7)
Location: MONTEVIEW
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter witnessed a rope tornado 15 miles south southwest of Mud Lake that quickly dissipated.

Thunderstorm Wind in CASSIA, IDAHO
From 31-MAY-18 15:45:00 to 31-MAY-18 16:00:00 (MST-7)
Location: ALMO
Magnitude: 63.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

The Goose Creek RAWS site measured a 73 mph wind gust.

Hail in JEFFERSON, IDAHO
From 31-MAY-18 16:11:00 to 31-MAY-18 16:20:00 (MST-7)
Location: ROBERTS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

An inch and a quarter sized hail fell in Roberts.

Funnel Cloud in FREMONT, IDAHO
From 31-MAY-18 16:46:00 to 31-MAY-18 17:00:00 (MST-7)
Location: PARKER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A funnel cloud reported by spotter west of Parker.

Hail in MADISON, IDAHO
From 31-MAY-18 16:49:00 to 31-MAY-18 17:00:00 (MST-7)
Location: REXBURG
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

One inch hail reported 4 miles west of Rexburg.

Funnel Cloud in JEFFERSON, IDAHO
From 31-MAY-18 16:20:00 to 31-MAY-18 16:25:00 (MST-7)
Location: ROBERTS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter reported a funnel cloud 13 miles west of Rexburg on highway 33 at mile marker 64.

Hail in JEFFERSON, IDAHO
From 31-MAY-18 16:20:00 to 31-MAY-18 16:28:00 (MST-7)
Location: ROBERTS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported 1 inch hail on Highway 33 at mile marker 64 thirteen miles west of Rexburg.

Hail in FREMONT, IDAHO
From 31-MAY-18 17:01:00 to 31-MAY-18 17:10:00 (MST-7)
Location: ST ANTHONY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

One inch hail reported in St Anthony.

Hail in FREMONT, IDAHO
From 31-MAY-18 17:47:00 to 31-MAY-18 18:00:00 (MST-7)
Location: ISLAND PARK
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

One inch hail reported at Island Park village Resort.

Funnel Cloud in BONNEVILLE, IDAHO
From 31-MAY-18 16:00:00 to 31-MAY-18 16:16:00 (MST-7)
Location: IDAHO FALLS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several photographs received of a funnel cloud west and northwest of Idaho Falls around 5 pm MDT.

Hail in MINIDOKA, IDAHO
From 31-MAY-18 14:00:00 to 31-MAY-18 14:15:00 (MST-7)
Location: RUPERT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

One inch hail in Rupert.

Hail in BONNEVILLE, IDAHO
From 31-MAY-18 11:30:00 to 31-MAY-18 11:40:00 (MST-7)
Location: AMMON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

One inch hail in Ammon.

Hail in JEFFERSON, IDAHO
From 31-MAY-18 19:00:00 to 31-MAY-18 19:10:00 (MST-7)
Location: ROBERTS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

One inch hail in Roberts.

Flash Flood in BONNEVILLE, IDAHO
From 31-MAY-18 16:00:00 to 31-MAY-18 17:00:00 (MST-7)
Location: IDAHO FALLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Extensive street flooding occurred from heavy rain from severe thunderstorms in Idaho Falls.   Minor basement flooding also occurred.

Hail in BONNEVILLE, IDAHO
From 31-MAY-18 16:00:00 to 31-MAY-18 16:15:00 (MST-7)
Location: IDAHO FALLS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

One inch hail near the Lowes in Idaho Falls.