Avalanche: Douglas Island

Location: False Troy / Troy Saddle

Date:
Observer:
Mark Krumwiede Professional
Route & General Observations

Standard route up Troy and to the saddle. We saw multiple crowns along Troy on the NNW aspect. A couple D1 sized storm slab were observed up close, one at about 2500′ on the west aspect with a 4-5in crown that was remotely triggered by previous skiers in the area. Temperature was colder in the morning, warming later in the day. Snow was most of the day. Also of note was another recent, naturally triggered, but larger wind slab avalanche on the NNW aspect of Troy. Size was about D1.5-2 which deposited large debris chunks at the bottom of the slope. It was in the clouds so was harder to get eyes on, but starting probably around ~2850′ and running a couple hundred feet down slope. Information in the Avalanche details section is for the remotely triggered soft slab slide heading up Troy saddle skin track.

Avalanche Details
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Trigger SkierAvalanche Type Soft Slab
Aspect NorthwestElevation 2500ft
Slope Angle 30degCrown Depth 4in
Width 35ftVertical Rununknown
Near Miss / Accident Details
Red Flags
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Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?Yes
Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

Calm wind in the trees on the skin track, switching to moderate strength winds at treeline coming out of the East. Snowing at a rate of about 1cm an hour, and temperature was 23 F, warming slightly towards the end of the day.

Snow surface

New snow

Snowpack

Pit was dug adjacent to a older storm slab crown convexity (naturally triggered last night or very early this morning, which was being refilled by the new snow/wind but crown was still visible).
Elevation: 2,694'
Aspect: West
Inlcline: 32 degrees
We conducted multiple ECTs and a CT and most collapsed upon isolation of test columns, results were at a very thin, pencil hard, wind slab layer buried 25cm.
Test results:
CTV, down 25cm
multiple ECTPV, down 25cm
ECTN 3, down 35cm
ECTN 14, down 55cm

In summary, very sensitive!

A hasty pit was dug at about 2200', of note were two fairly dense wind slab layers, 25cm below the surface, each 5cm thick. Compression tests results were easily to moderately triggered.
Keep in mind, spatial variability in the snowpack across elevation and distance.

Photos & Video
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Troy Saddle -09-Jan  

The thin wind packed layer 25cm below the surface  

Location