Island Park

Snowmobile Triggered Avalanche in Black Canyon

Date
Activity
Snowmobiling

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.”

Region
Island Park

Poor Structure and Collapsing, Centennials

Centennials - Montana
Island Park
Code
Latitude
44.56530
Longitude
-111.80300
Notes

From obs: "Spent a day digging out the Hut in the Centennial Saturday 1/20. Our hasty pit, 20 deg. SW aspect at 7,000’ about 1/2 way into the hut showed 75 cm snow depth and various sized facets to a depth of 45 cm from the ground overlain by new snow. The structure was poor, and weak but we did not observe propagation in an ECT. Snow surfaces were damp on all aspect that we touched below 8,000’, pin wheel rollers on many steep slopes could be seen near the creek. Plenty of collapsing and “whumfing” on the way in kept us wary. Snow depths below 7,000 feet were as shallow as I have seen in 10 years operating the hut."

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

Poor Structure and Variable Depth/Conditions in Hellroaring

Date
Activity
Skiing

Spent a day digging out the Hut in the Centennial Saturday 1/20. Our hasty pit, 20 deg. SW aspect at 7,000’ about 1/2 way into the hut showed 75 cm snow depth and various sized facets to a depth of 45 cm from the ground overlain by new snow. The structure was poor, and weak but we did not observe propagation in an ECT. Snow surfaces were damp on all aspect that we touched below 8,000’, pin wheel rollers on many steep slopes could be seen near the creek. Plenty of collapsing and “whumfing” on the way in kept us wary. Snow depths below 7,000 feet were as shallow as I have seen in 10 years operating the hut.

Region
Island Park
Location (from list)
Centennials - Montana
Observer Name
Sam Hansen

Snowmobiler triggered slide, Island Park

Sawtelle Peak
Island Park
Code
SS-R2-D2-O
Elevation
9600
Aspect
SE
Latitude
44.56110
Longitude
-111.44300
Notes

A snowmobiler triggered slide occurred yesterday below Sawtelle Peak. It broke on the buried surface hoar and facets about 1.5 feet under the surface. 

The avalanche:

44.55581, -111.45085
El 9,286'
 
HS - 143 cm
Surf hoar 96-95 cm
Slab was 18-24" deep
Not really wind loaded, but it looks like winds wrap around that face.
About 150' wide
about 300' vertical
Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
50.0 centimeters
Vertical Fall
300ft
Slab Width
150.00ft
Weak Layer Grain type
Surface Hoar
Weak Layer Hardness
F
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

On Sawtelle Peak, Island Park, when the clouds lifted we could see a crown of a snowmobiler triggered slide that occurred yesterday. It broke on the buried surface hoar and facets about 1.5 feet under the surface. Recent snow and wind-loading has created dangerous avalanche conditions. Photo: GNFAC

Island Park, 2024-01-19

On Sawtelle Peak, Island Park, when the clouds lifted we could see a crown of a snowmobiler triggered slide that occurred yesterday. It broke on the buried surface hoar and facets about 1.5 feet under the surface. Recent snow and wind-loading has created dangerous avalanche conditions. Photo: GNFAC

Island Park, 2024-01-19

On Sawtelle Peak, Island Park, when the clouds lifted we could see a crown of a snowmobiler triggered slide that occurred yesterday. It broke on the buried surface hoar and facets about 1.5 feet under the surface. Recent snow and wind-loading has created dangerous avalanche conditions. Photo: GNFAC

Island Park, 2024-01-19

An avalanche and instability

Date
Activity
Snowmobiling

We dug pits and rode on Sawtelle Peak. At 9,100 feet we had unstable test results (ECTP13 x 5; ECTP10 x2; CT4, Q1). When the clouds lifted we could see a crown of a snowmobiler triggered slide that occured yesterday. It broke on the buried surface hoar and facets about 1.5 feet under the surface. Recent snow and wind-loading has created dangerous avalanche conditions.

The avalanche:

44.55581, -111.45085
El 9,286'
 
HS - 143 cm
Surf hoar 96-95 cm
Slab was 18-24" deep
Not really wind loaded, but it looks like winds wrap around that face.
About 150' wide
about 300' vertical
Region
Island Park
Location (from list)
Sawtelle Peak
Observer Name
Doug Chabot