Avalanche: Turnagain

Location: Seattle Ridge

Route & General Observations

Toured up to Seattle ridge on the normal motorized uptrack to about 3000′. Had pretty good visibility to observe avalanches across the valley on the skiers side and other than 1 recent avalanche further north along Seattle ridge we did not observe any other activity besides some dry loose avalanches in steep terrain.

Avalanche Details
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Trigger NaturalRemote Trigger Unknown
Avalanche Type UnknownAspect West
Elevation 2700ftSlope Angleunknown
Crown Depth 12inWidthunknown
Vertical Run 150ft  
Avalanche Details

Observed what looked like a fresh wind slab that released naturally. We were pretty far away. My guess is that it released all or most of the new snow (about 12" + some wind loading). Very soft slab that did not run very far. The crown ran along a steep convexity on a wind loaded aspect of Seattle Ridge.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.

Clouds cleared out as we were driving up to Turnagain, leaving just a layer of higher clouds above the ridge tops. Light winds. There was about 14" of moist new snow at the parking lot which got drier as we climbed.

Snow surface

30-35cm (12+") of new snow. Moist at the road elevations with a very thin crust on the surface. The new snow dried out at about 2000'. There was some wind transport in the new snow from 2500-3000' along the ridgetop, but not much.


We dug a pit at 2400' that had about 30cm (12") of moist new snow over a fairly strong melt freeze crust. The crust was about 5cm thick and below that the snowpack was wet for about 30cm. This wet layer underneath the crust was pretty weak and we had full propagation in our ECT below the crust where it transitioned to wet snow. We found the basal facets in this pit but they were moist and did not show any signs of instability in our tests.

At 2800' we dug another pit and found drier new snow with some light wind transport. The ~5cm thick melt freeze crusts existed here as well at about 35cm down (14"). Below the melt freeze crust the snowpack was much stronger than in the 2400' pit. With a few additional thin crusts intermixed with strong rounded snow. We found the layer of basal facets on the ground but did not have any test results indicating that they were reactive in this location.

Photos & Video
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