Snowcat triggered avalanche in Swan Creek
Swan Creek
Northern Gallatin
Code
SS-AKu-R3-D3-O
Elevation
7800
Aspect
W
Latitude
45.37610
Longitude
-111.09400
Notes
GNFAC investigation: We went and looked at the avalanche that partially buried a groomer without injury to the driver at 8:15 p.m. the night before (2/27). The slide broke on facets at the ground and was 2-3' deep, 100' wide, and ran 600' slope distance. It put 8' of debris on the road cut. The slope was west facing at 7,500' and averaged 38 degree steep in the starting zone. Weak snow at the ground is found throughout our advisory area.
The groomer triggered the avalanche when he was clearing a wind drift from the road. The groomer is badly damaged.
Crown: N45.38528, W111.06487, 7802 feet
Toe of debris: N45.38554, W111.06693, 7482 feet
Alpha Angle: 30 degrees
Billings Gazette Article HERE.
Number caught
1
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowcat
Trigger Modifier
u-An unintentional release
R size
3
D size
3
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
36.0 inches
Vertical Fall
400ft
Slab Width
130.00ft
Weak Layer Grain type
Depth Hoar
Weak Layer grain size
2.00mm
Weak Layer Hardness
F
Slab Layer Grain Type
Rounded Grains
Slab Layer Grain Size
1.00mm
Slab Layer Hardness
1F
Images
Attached Videos
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year