Island Park

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Bridger Range, 2024-01-25

Cracking and Collapsing in Black Canyon, Island Park

Other place
Island Park
Code
Latitude
44.47670
Longitude
-111139000.00000
Notes

From obs: "Collapsing snow could be felt underneath my sled all day up Black Canyon Loop trail, east of Island Park. There was a moment where shooting cracks spread from my ski tips to about 10 yards away on flat ground. The canyon just north my location was probably steep enough to slide."

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

Serious signs of instability up black canyon

Date
Activity
Snowmobiling

Collapsing snow could be felt underneath my sled all day up Black Canyon Loop trail, east of Island Park. There was a moment where shooting cracks spread from my ski tips to about 10 yards away on flat ground. The canyon just north my location was probably steep enough to slide.

Region
Island Park
Location (from list)
Other place
Observer Name
Marcus Sirounian

Natural Avalanche Lionhead Ridge

Lionhead Ridge
Lionhead Range
Code
SS-N-R1-D1.5-O
Aspect
E
Latitude
44.71450
Longitude
-111.31800
Notes

Riders spotted a small natural avalanche on Lionhead Ridge. The slide occurred in the morning of January 21. Unknown dimensions, but weak layers in the area are buried ~18" deep, and the slide appears relatively small. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1.5
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 inches
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Natural Avalanche Ski Hill

Ski Hill
Lionhead Range
Code
SS-N-R2-D2-O
Elevation
7950
Aspect
E
Latitude
44.70160
Longitude
-111.29300
Notes

A natural avalanche broke on January 21 on Brady's Slope on Ski Hill. Walking to look at the avalanche, we triggered a large collapse and shooting cracks. We dug a pit nearby and got very unstable test results (ECTP4) on a layer of 15-20 mm surface hoar buried 18" deep. Avalanche width and vertical fall were estimated based on Google Earth measurements.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 inches
Vertical Fall
300ft
Slab Width
200.00ft
Weak Layer Grain type
Surface hoar crystals
Weak Layer grain size
15.00mm
Weak Layer Hardness
F-
Slab Layer Grain Type
Precipitation Particles
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Snowmobile Triggered Avalanche in Black Canyon

Island Park
Code
SS-AMu-R3-D2-O
Latitude
44.54760
Longitude
-111.23900
Notes

From interaction at the gas station:

“We were riding out from Island Park. We saw dramatic, collapses, and shooting cracks. I side-hilled a small slope and triggered it 1.5 to 2 feet deep. I have never seen such unstable snow.”

The avalanche likely failed on a layer of surface hoar widespread in the Lionhead and Island Park areas. The avalanche buried part of the groomed road that crosses below this slope. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 inches
Vertical Fall
50ft
Slab Width
100.00ft
Weak Layer Grain type
Surface Hoar
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year