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Storm slab cycle in the southern Whitefish Range
Location Name:
Forecaster Observation - Canyon Creek, Whitefish Range
Observation date:
Wednesday, December 12, 2018 - 14:45
Is this an Avalanche Observation:
Yes
Observation made by:
Forecaster
Location
Tabs
Quick Observation
A natural storm slab avalanche cycle occurred on sunny and shaded aspects at mid-elevations Tuesday night/Wednesday morning. Most of the slides ran early in the storm and were covered with 6"+ of new snow. Slides failed approximately 1 foot below the surface at the new snow/old snow interface. Slides were mostly small D 1-1.5 with several D2.
New snow, up to 12" in depth, was dense and overloaded the well advertised weak surface snow. Textbook!
The snowpack was reactive to my weight with a number of shooting cracks (up to 20'+) and collapses.
Substantial wind transport occurred at mid and upper elevations throughout the day.
Snowpack, Avalanche, Weather Images:
Travel Details
Region:
Whitefish Range - Southern (south of Coal Creek)
Route Description:
East of the ski area
Snowpack Details
Snowpack and Weather Details:
Terrain
Elevation of observation:
5000-6500 ft
Above 6500 ft
Aspect(s) of observation:
N
NE
E
S
Red Flags:
Shooting cracks
Collapsing / whumpfing noises
More than a foot of new snow or heavy snowfall rates (>1"/hr)
Blowing snow
Persistent Weak Layers:
Surface Hoar
Facets or Faceted Crust
On the surface
Buried
New Snow in the past 24 hours:
12.00in.
Total Snow Depth:
30
Blowing Snow:
Moderate
Wind Speed:
Moderate (Small trees sway)
Wind Direction:
Southwest
Air temperature:
Below Freezing
Snow line:
2000
Sky Cover:
Overcast (OVC)
Avalanche Details
Avalanche Details:
Date and Time of Avalanche:
Wednesday, December 12, 2018 - 01:45
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
New/old snow interface
Trigger
Trigger:
natural
Terrain
Start Zone Slope Angle:
35
Size
Destructive Size:
D1.5
Relative Size:
R2 Small
Crown Height:
1 ft
Avalanche Length (Vertical Run):
100ft.
Avalanche Width (Average width):
50ft.
Avalanche Location:
Javascript is required to view this map.
Date and Time of Avalanche:
Wednesday, December 12, 2018 - 20:30
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
New/old snow interface
Trigger
Trigger:
natural
Terrain
Start Zone Slope Angle:
35
Aspect:
South
Starting Elevation:
above-treeline
Size
Destructive Size:
D2 Could bury, injure, or kill a person.
Relative Size:
R2 Small
Crown Height:
1 ft
Avalanche Length (Vertical Run):
500ft.
Avalanche Width (Average width):
100ft.
Avalanche Location:
Javascript is required to view this map.
Date and Time of Avalanche:
Wednesday, December 12, 2018 - 20:45
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
New/old snow interface
Trigger
Trigger:
natural
Terrain
Start Zone Slope Angle:
35
Aspect:
East
Starting Elevation:
above-treeline
Size
Destructive Size:
D2 Could bury, injure, or kill a person.
Relative Size:
R2 Small
Crown Height:
1 ft
Avalanche Length (Vertical Run):
200ft.
Avalanche Width (Average width):
150ft.
Avalanche Location:
Javascript is required to view this map.
