Widespread storm slabs in Spider Bowl
Location Name: Forecaster Observation - Spider Bowl, Swan Range Observation date: Thursday, December 28, 2017 - 15:30 |
Is this an Avalanche Observation: Yes |
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Observation made by: Forecaster
Location
Tabs
Avalanche Details:
Date and Time of Avalanche:
Thursday, December 28, 2017 - 12:30
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
Within storm snow
Trigger:
skier
Destructive Size:
D1 Relatively harmless to people.
Relative Size:
R1 Very Small
Crown Height:
Less than 1 ft
Avalanche Location:
Date and Time of Avalanche:
Thursday, December 28, 2017 - 11:45
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
Within storm snow
More information or comments about the avalanche:
Most naturals were above 6,000 ft. A handful of naturals at lower elevations on very steep slopes. Crown sizes from 5" to 10", breaking on low density stellar dendrite layer that fell 12/27.
Trigger:
natural
Starting Elevation:
above-treeline
Destructive Size:
D1.5
Relative Size:
R1 Very Small
Crown Height:
Less than 1 ft
Avalanche Length (Vertical Run):
500ft.
Avalanche Location:
Date and Time of Avalanche:
Tuesday, December 19, 2017 - 21:45
Avalanche Type:
Soft Slab
More information or comments about the avalanche:
Evidence that at least some portion of Spider Bowl ran on the Thanksgiving Crust during last week's cycle. The NW facing start zone had lost the PS structure and there was a D2.5 debris pile 2000 feet below. Unsure of how wide the slide propagated.
Trigger:
natural
Aspect:
Northwest
Starting Elevation:
above-treeline
Destructive Size:
D2.5
Relative Size:
unknown
Avalanche Length (Vertical Run):
2000ft.
Avalanche Location:
All elevations. Crown sizes from 5" to 10", breaking on low density stellar dendrite layer that fell 12/27. Impressive remote triggering for a Fist-hard soft slab. As much as 300 feet away.