20-21

Remotely triggered cracking in Bridgers

Texas Meadow
Bridger Range
Code
Latitude
45.84270
Longitude
-110.93700
Notes

From obs: "the whumpf I had heard previously remotely triggered a series of 7-8 large cracks that ranged from 30-100 feet wide. ... As I carefully descended the meadow, I saw many more cracks throughout the slope from the same remote trigger event. Additionally, I triggered two more significant whumpfs with shooting cracks 10-40 feet wide. We determined our remote trigger was at least 300 feet away from where the snow collapsed and cracked"

Number of slides
0
Number caught
0
Number buried
0
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year

From obs: "the whumpf I had heard previously remotely triggered a series of 7-8 large cracks that ranged from 30-100 feet wide. ... As I carefully descended the meadow, I saw many more cracks throughout the slope from the same remote trigger event. Additionally, I triggered two more significant whumpfs with shooting cracks 10-40 feet wide. We determined our remote trigger was at least 300 feet away from where the snow collapsed and cracked"

Photo: L. Ippolito

Bridger Range, 2021-01-08

Skier Triggered Avalanche near Meridian Peak

Cooke City
Code
SS-ASu-R2-D1.5
Elevation
9350
Aspect
SE
Latitude
45.02700
Longitude
-110.00300
Notes

From observation (1/8/21): "Skier triggered slide from someone outside our group lower in Silver Creek 9350’ S facing 18-24” deep 60-70’ wide. Ran 500’ skier was able to regain skis and off slab 100’ below initiation."

Number of slides
1
Number caught
1
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
2
D size
1.5
Slab Thickness
20.0 inches
Vertical Fall
500ft
Slab Width
60.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Remote triggered slide Cinnamon Creek

Southern Madison
Code
R2-D2.5
Elevation
9000
Aspect
E
Latitude
45.12740
Longitude
-111.26600
Notes

From obs: "Shooting cracks and collapsing on the entire ascent to the Cinnamon Creek Lookout. Remotely triggered a R2-D2.5 on descent. 2-3 foot crown. Slide path was on an East facing slope at 9000ft. Failed on the same persistent weak layer being seen across most regions of the forecast zone."

Number of slides
1
Number caught
0
Number buried
0
R size
2
D size
2.5
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs: "Shooting cracks and collapsing on the entire ascent to the Cinnamon Creek Lookout. Remotely triggered a R2-D2.5 on descent. 2-3 foot crown. Slide path was on an East facing slope at 9000ft. Failed on the same persistent weak layer being seen across most regions of the forecast zone."

Southern Madison, 2021-01-08

Natural avalanche near Fairy Lake

Fairy Lake
Bridger Range
Code
HS-R2-D2.5
Latitude
45.90910
Longitude
-110.97700
Notes

Large natural avalanche north of Hardscrabble Peak near Fairy Lake. Likely broke during snowfall/wind on Thursday, Jan 7th.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
R size
2
D size
2.5
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Many whumpfs/Collapses in N. Madison

NORTHERN MADISON RANGE
Northern Madison
Code
Latitude
45.29380
Longitude
-111.32100
Notes

From obs (1/8/21): "Loud whoomphs and collapses while skinning uphill, from the car until we turned around about 400ft below the summit. Snowpack felt extremely responsive and we carefully avoided all avalanche terrain."

Number of slides
0
Number caught
0
Number buried
0
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year

Skier triggered, caught and injured on The Fin

The Fin
Cooke City
Code
SS-ASu-R2-D2.5-O
Elevation
9700
Aspect
E
Latitude
45.00460
Longitude
-109.95800
Notes

FULL AVALANCHE REPORT: https://www.mtavalanche.com/accident/21/01/11

On January 8, 2021 a group of six skiers triggered an avalanche on The Fin on Republic Mountain outside of Cooke City. They were skinning up the slope when they felt the slope collapse and watched cracks propagate 250’ upslope. Three were caught and partially buried. Skier 1 deployed his airbag, was partially buried and able to get himself free. He freed himself from the debris and began a beacon search which led him to see skier 2 who was buried head down with his airway obstructed. He was uncovered by skier 1, not breathing and unconscious. He sustained injuries, but later made it out under his own power. Skier 3 was partially buried higher in the path, sustained serious injuries to his ribs and lungs and was evacuated by helicopter. The avalanche broke 1.5’- 2’ deep, 200’ wide and ran 700’ vertical. The average slope angle was 37 degrees. Slope angle at the crown was 33 degrees on an east aspect at 9,700’ elevation. The avalanche is classified SS-ASu-R2-D2.5-O.

 

Number of slides
1
Number caught
3
Number buried
1
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
2
D size
2.5
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 inches
Vertical Fall
700ft
Slab Width
200.00ft
Weak Layer Grain type
Faceted Crystals
Weak Layer grain size
2.00mm
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year