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Wind slabs and deep slabs in Skiumah
Location Name:
Forecaster Observation - Skiumah Lake, Flathead Range
Observation date:
Thursday, February 1, 2018 - 18:30
Is this an Avalanche Observation:
Yes
Observation made by:
Forecaster
Tabs
Quick Observation
6" of new, low-density snow and graupel over the most recent rain/sun crust. The crust thins by around 6,000'. Not enough snow or cohesion for avalanche concerns in the new snow except in wind-loaded areas. We observed shooting cracks and triggered shallow wind slabs on wind-loaded rollovers, D1 in size. These were breaking on mid-storm layers above the crust or storm interface. Drifts were up to 10" thick at mid and upper elevations.
One D3 came off of the north face of Mt Penrose towards the end of the last storm, and a number of smaller wet loose and dry debris piles.
I investigated the cornice triggered deep slab that was triggered on Tuesday. I updated
this observation
with photos and details. It was an 8-foot hard slab that failed on facets above the Thanksgiving crust.
Snowpack, Avalanche, Weather Images:
Snowpack, Avalanche, Weather Videos:
February 1, 2018. Wind slabs and deep slabs in Skiumah
Video of February 1, 2018. Wind slabs and deep slabs in Skiumah
Travel Details
Region:
Flathead Range - Middle Fork Corridor
Route Description:
Skiumah Lake to Upper Basin to 6,800'
Activity:
Skiing
Snowpack Details
Snowpack and Weather Details:
Terrain
Elevation of observation:
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation:
N
NE
Red Flags:
Shooting cracks
Blowing snow
Persistent Weak Layers:
Buried
New Snow in the past 24 hours:
5.00in.
Total Snow Depth:
250
Avalanche Details
Avalanche Details:
Date and Time of Avalanche:
Saturday, January 27, 2018 - 22:30
Avalanche Type:
Unknown
Failure Plane/Weak Layer:
Unknown
Trigger
Trigger:
natural
Terrain
Aspect:
North
Starting Elevation:
above-treeline
Size
Destructive Size:
D3 - Could destroy a car, a wood house, or snap trees
Avalanche Location:
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Date and Time of Avalanche:
Thursday, February 1, 2018 - 13:45
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
Within storm snow
Trigger
Trigger:
skier
Trigger Modifier:
Intentionally Triggered
Terrain
Aspect:
Northeast
Starting Elevation:
above-treeline
Size
Destructive Size:
D1 Relatively harmless to people.
Relative Size:
R1 Very Small
Crown Height:
Less than 1 ft
Avalanche Location:
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Date and Time of Avalanche:
Monday, January 29, 2018 - 13:45
Avalanche Type:
Wet Loose
Failure Plane/Weak Layer:
Within storm snow
Trigger
Trigger:
natural
Terrain
Starting Elevation:
near-treeline
Size
Destructive Size:
D1.5
Relative Size:
R1 Very Small
Avalanche Location:
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