A few severe thunderstorms impacted portions of the Billings Forecast Area during the early and mid afternoon hours of the 21st. Thunderstorms developed over the Beartooth/Absaroka Foothills and intensified as they moved off the foothills. One particular thunderstorm became severe over Central Carbon County before moving northeast into Yellowstone County. The storm impacted mainly the west and northwest sides of the city of Billings where hail ranged in size from pea to tennis ball size. There was a swath of golf ball size hail with a few the size of tennis balls across the northwest and north areas of the city of Billings.  Winds at the beginning of the storm gusted to 66 mph at the Billings Airport, but the majority of the hail core was not associated with these winds. Substantial damage to structures and vehicles was reported. In addition, three people were injured at the Billings Rod and Gun Club and treated for lacerations at the Billings Clinic. The storm caused two storm outages in Billings as firefighters responded to a few downed power and cable lines, mainly along and west and north of 24th Street West. In addition, some area car dealerships saw damage to their vehicles.
The storm developed into a well-defined supercell just northeast of Billings in Yellowstone County and moved into northeast Yellowstone and southeast Musselshell Counties where a well-defined hook echo developed and a funnel cloud was reported.
This supercell thunderstorm then produced a tornado about 16 miles north of Pompeys Pillar located in northeast Yellowstone County. In addition, significant wind damage occurred south of the supercell track in clear air near the town of Hysham in Treasure County. This was likely the result of the cold pool propagating downstream along the Yellowstone River Valley.

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:17:00 to 21-MAY-16 14:17:00 (MST-7)
Location: SHEPHERD
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STILLWATER, MONTANA
From 21-MAY-16 13:20:00 to 21-MAY-16 13:20:00 (MST-7)
Location: COLUMBUS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:03:00 to 21-MAY-16 14:03:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in STILLWATER, MONTANA
From 21-MAY-16 13:15:00 to 21-MAY-16 13:15:00 (MST-7)
Location: COLUMBUS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:01:00 to 21-MAY-16 14:01:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STILLWATER, MONTANA
From 21-MAY-16 13:05:00 to 21-MAY-16 13:05:00 (MST-7)
Location: COLUMBUS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in CARBON, MONTANA
From 21-MAY-16 13:05:00 to 21-MAY-16 13:05:00 (MST-7)
Location: ROBERTS BANGART ARPT
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in YELLOWSTONE, MONTANA
From 21-MAY-16 14:50:00 to 21-MAY-16 14:55:00 (MST-7)
Location: POMPEYS PILLAR
Tornado F-scale: EF1
Reported by: COOP Observer

A tornado occurred about 16 miles north of Pompeys Pillar during the afternoon of the 21st. The tornado was on the ground for about 5 minutes and was 150 yards wide with a path length of 2 miles. Approximately 100 pine trees were either uprooted or snapped off. Two power poles were also snapped off with downed power lines. This tornado was rated an EF-1 with wind speeds of 90 to 100 mph.

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in CARBON, MONTANA
From 21-MAY-16 13:05:00 to 21-MAY-16 13:05:00 (MST-7)
Location: ROBERTS BANGART ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:15:00 to 21-MAY-16 14:15:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:10:00 to 21-MAY-16 14:10:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in ROSEBUD, MONTANA
From 21-MAY-16 17:50:00 to 21-MAY-16 17:50:00 (MST-7)
Location: ROCK SPGS
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:59:00 to 21-MAY-16 13:59:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in ROSEBUD, MONTANA
From 21-MAY-16 17:04:00 to 21-MAY-16 17:04:00 (MST-7)
Location: FORSYTH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:59:00 to 21-MAY-16 13:59:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in ROSEBUD, MONTANA
From 21-MAY-16 17:00:00 to 21-MAY-16 17:00:00 (MST-7)
Location: FORSYTH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:55:00 to 21-MAY-16 13:55:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 14:00:00 to 21-MAY-16 14:00:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in MUSSELSHELL, MONTANA
From 21-MAY-16 15:30:00 to 21-MAY-16 15:30:00 (MST-7)
Location: MELSTONE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:52:00 to 21-MAY-16 13:52:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in TREASURE, MONTANA
From 21-MAY-16 15:27:00 to 21-MAY-16 15:27:00 (MST-7)
Location: HYSHAM
Magnitude: 70.00 EG
Reported by: NWS Storm Survey

A supercell thunderstorm moved rapidly northeast across far northwestern Treasure County. This storm then put out an outflow boundary that raced eastward across central Treasure County into the Yellowstone River Valley. An area of enhanced wind, estimated at 80 mph, developed in an area just north of Hysham northward to the Yellowstone River.  It���s estimated that upwards of 50 trees were either uprooted or snapped off. In addition, a mobile home was pushed off its blocks and a small garage (poorly constructed) was destroyed but contents left in place. Another home had numerous evergreens uprooted with damage to a garage and shed.

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:51:00 to 21-MAY-16 13:51:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in MUSSELSHELL, MONTANA
From 21-MAY-16 15:10:00 to 21-MAY-16 15:10:00 (MST-7)
Location: MUSSELSHELL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:47:00 to 21-MAY-16 13:47:00 (MST-7)
Location: LAUREL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in MUSSELSHELL, MONTANA
From 21-MAY-16 15:10:00 to 21-MAY-16 15:10:00 (MST-7)
Location: MUSSELSHELL
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 21-MAY-16 13:45:00 to 21-MAY-16 13:45:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in MUSSELSHELL, MONTANA
From 21-MAY-16 14:45:00 to 21-MAY-16 14:45:00 (MST-7)
Location: GAGE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CARBON, MONTANA
From 21-MAY-16 13:30:00 to 21-MAY-16 13:30:00 (MST-7)
Location: JOLIET
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public