A southeast low-level surface flow advected very moist air from the central plains westward across southeast and south-central Montana. Dewpoints were in the 50s to lower 60s across the Billings Forecast Area. At the same time,  a very strong jet max moved across central and south central Montana. In addition to the above, lapse rates were steep across the area along with high CAPE values. Strong speed and directional shear was in place over the Billings forecast area resulting in organized, rotating updrafts. As a result, storms across the area produced very large hail and damaging winds.
Significant damage was done to Shepherd schools. There was roof damage and extensive damage to the bus barn. In addition, all the west side windows were broken out from combined hail and wind.
Storm damage also occurred to a few commercial planes at the Billings Airport. Frontier and Alaska Airlines both had planes damaged by the hailstorm. In addition, fallen trees and branches knocked out power to about 1,500 residents and emergency crews responded to a car wreck in the Heights with reports of people trapped in an elevator.
The storm also destroyed one-third of the barley and wheat crop, approximately $400,000 worth,  at a farm in Molt.
In addition, The storm killed and maimed 11,000 to 13,000 waterfowl and wetland birds at the Big Lake Wildlife Management Area west of Molt. Montana Fish, Wildlife & Parks biologists picked up dead ducks and shorebirds with broken wings, smashed skulls, and internal damage and other injuries consistent with massive blunt-force trauma. They reported thousands of additional dead or badly injured waterfowl and wetland birds in and around the lake. An estimated 20 to 30 percent of the birds at the lake were killed or injured.

Hail in SWEET GRASS, MONTANA
From 11-AUG-19 13:56:00 to 11-AUG-19 13:56:00 (MST-7)
Location: MELVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in STILLWATER, MONTANA
From 11-AUG-19 17:35:00 to 11-AUG-19 17:35:00 (MST-7)
Location: WHEAT BASIN
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Car windshields were broken along with four house windows.

Hail in BIG HORN, MONTANA
From 11-AUG-19 18:53:00 to 11-AUG-19 18:53:00 (MST-7)
Location: KIRBY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:14:00 to 11-AUG-19 18:14:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A 2 foot diameter tree was downed on a golf course.

Hail in STILLWATER, MONTANA
From 11-AUG-19 14:16:00 to 11-AUG-19 14:16:00 (MST-7)
Location: REED PT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STILLWATER, MONTANA
From 11-AUG-19 17:41:00 to 11-AUG-19 17:41:00 (MST-7)
Location: MOLT
Magnitude: 2.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 17:50:00 to 11-AUG-19 17:50:00 (MST-7)
Location: ACTON
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Wooden fence posts were broken and a steel post was bent. Large tree limbs were down and windows in a home were broken.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:15:00 to 11-AUG-19 18:15:00 (MST-7)
Location: BILLINGS
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 17:55:00 to 11-AUG-19 17:55:00 (MST-7)
Location: ACTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Some broken tree limbs were reported on 27th street.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:21:00 to 11-AUG-19 18:21:00 (MST-7)
Location: SHEPHERD
Magnitude: 61.00 EG
Property damage: 2.50M
Crop damage: 0.00K
Reported by: Public

Significant damage was done to Shepherd schools. There was roof damage and extensive damage to the bus barn. In addition, all the west side windows were broken out from combined hail and wind.

Hail in SWEET GRASS, MONTANA
From 11-AUG-19 14:56:00 to 11-AUG-19 14:56:00 (MST-7)
Location: MELVILLE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:03:00 to 11-AUG-19 18:03:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 17:50:00 to 11-AUG-19 17:50:00 (MST-7)
Location: ACTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Wooden fence posts were broken along with a steel post being bent. Large tree limbs were down and windows in a home were broken.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:21:00 to 11-AUG-19 18:21:00 (MST-7)
Location: SHEPHERD
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Multiple 1 to 1.5 foot diameter trees were snapped.

Hail in GOLDEN VALLEY, MONTANA
From 11-AUG-19 15:14:00 to 11-AUG-19 15:14:00 (MST-7)
Location: FRANKLIN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:05:00 to 11-AUG-19 18:05:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:07:00 to 11-AUG-19 18:07:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Tree limbs approximately 1.5 feet in diameter were broken.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:21:00 to 11-AUG-19 18:21:00 (MST-7)
Location: SHEPHERD
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A roof was partially collapsed.

Hail in WHEATLAND, MONTANA
From 11-AUG-19 15:45:00 to 11-AUG-19 15:45:00 (MST-7)
Location: SHAWMUT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:05:00 to 11-AUG-19 18:05:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:08:00 to 11-AUG-19 18:08:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A tree was down on a road.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:21:00 to 11-AUG-19 18:21:00 (MST-7)
Location: LOCKWOOD
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Tree branches 6 inches in diameter were broken.

Hail in SWEET GRASS, MONTANA
From 11-AUG-19 16:27:00 to 11-AUG-19 16:27:00 (MST-7)
Location: BIG TIMBER
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:08:00 to 11-AUG-19 18:08:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:09:00 to 11-AUG-19 18:09:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A 16 diameter Ponderosa Pine tree fell on the roof of a house.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:23:00 to 11-AUG-19 18:23:00 (MST-7)
Location: HUNTLEY
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A tree, approximately 1.5 feet in diameter, was uprooted.

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:11:00 to 11-AUG-19 18:11:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 3.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:08:00 to 11-AUG-19 18:08:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: LAUREL
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A tree approximately 6 inches in diameter was downed.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:30:00 to 11-AUG-19 18:30:00 (MST-7)
Location: HUNTLEY
Magnitude: 59.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:13:00 to 11-AUG-19 18:13:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in SWEET GRASS, MONTANA
From 11-AUG-19 14:16:00 to 11-AUG-19 14:16:00 (MST-7)
Location: MELVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:33:00 to 11-AUG-19 18:33:00 (MST-7)
Location: BALLANTINE
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large tree limbs were blown down.

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:14:00 to 11-AUG-19 18:14:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 17:55:00 to 11-AUG-19 17:55:00 (MST-7)
Location: ACTON
Magnitude: 64.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A Russian Olive tree roughly 8 inches in diameter was damaged.

Thunderstorm Wind in ROSEBUD, MONTANA
From 11-AUG-19 19:55:00 to 11-AUG-19 19:55:00 (MST-7)
Location: FORSYTH
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Some tree damage was reported.

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:17:00 to 11-AUG-19 18:17:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:03:00 to 11-AUG-19 18:03:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ROSEBUD, MONTANA
From 11-AUG-19 20:30:00 to 11-AUG-19 20:30:00 (MST-7)
Location: BRANDENBERG
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:20:00 to 11-AUG-19 18:20:00 (MST-7)
Location: SHEPHERD
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The winds were estimated to be 50 to 60 mph.

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:09:00 to 11-AUG-19 18:09:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Severe wind gusts lasted over 10 minutes.

Thunderstorm Wind in ROSEBUD, MONTANA
From 11-AUG-19 20:30:00 to 11-AUG-19 20:30:00 (MST-7)
Location: HATHAWAY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:24:00 to 11-AUG-19 18:24:00 (MST-7)
Location: HUNTLEY
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:33:00 to 11-AUG-19 18:33:00 (MST-7)
Location: BALLANTINE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large tree limbs were blown down.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A car hood was dented, as well as siding on a house.

Thunderstorm Wind in CUSTER, MONTANA
From 11-AUG-19 20:43:00 to 11-AUG-19 20:43:00 (MST-7)
Location: MILES CITY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in SWEET GRASS, MONTANA
From 11-AUG-19 16:30:00 to 11-AUG-19 16:30:00 (MST-7)
Location: BIG TIMBER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:35:00 to 11-AUG-19 18:35:00 (MST-7)
Location: WORDEN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: BILLINGS LOGAN ARPT
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tree limbs were broken on 27th street.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:12:00 to 11-AUG-19 18:12:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

There was significant tree damage reported. Several 10 to 12 inch diameter tree limbs were downed. Minor roof damage along with blown off shingles to a house was reported.

Hail in SWEET GRASS, MONTANA
From 11-AUG-19 16:31:00 to 11-AUG-19 16:31:00 (MST-7)
Location: BIG TIMBER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YELLOWSTONE, MONTANA
From 11-AUG-19 18:35:00 to 11-AUG-19 18:35:00 (MST-7)
Location: WORDEN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winds were estimated in excess of 60 mph. The combination of the wind and hail blew out several windows.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:10:00 to 11-AUG-19 18:10:00 (MST-7)
Location: LAUREL MUNI ARPT
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:35:00 to 11-AUG-19 18:35:00 (MST-7)
Location: WORDEN
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The wind and hail blew out several windows.

Hail in PARK, MONTANA
From 11-AUG-19 13:06:00 to 11-AUG-19 13:06:00 (MST-7)
Location: GRANNIS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STILLWATER, MONTANA
From 11-AUG-19 16:55:00 to 11-AUG-19 16:55:00 (MST-7)
Location: REED PT
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BIG HORN, MONTANA
From 11-AUG-19 18:39:00 to 11-AUG-19 18:39:00 (MST-7)
Location: GARRYOWEN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 11-AUG-19 18:12:00 to 11-AUG-19 18:12:00 (MST-7)
Location: BILLINGS HGTS
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Tree branches approximately 8 inches in diameter fell on a roof.