Avalanche: Turnagain

Location: Tincan Trees

Route & General Observations

Tincan Trees to 2200′

Avalanche Details
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Trigger SkierRemote Trigger Unknown
Avalanche Type Soft SlabAspect Northwest
Elevation 2000ftSlope Angle 38deg
Crown Depth 12inWidthunknown
Vertical Rununknown  
Avalanche Details

Small (D1) skier triggered soft slab breaking within recent new snow on a steep rollover at Tincan Treeline; crown looked to be ~1' deep at most, and a photo of debris is below. On similar terrain features steeper than 38 degrees, small slabs just slightly longer than ski length would occasionally break, but nothing else notable observed below treeline.

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?No
Observer Comments

Obscured skies made for limited visibility in the alpine and on neighboring peaks throughout our day, but in one clear break several D1 loose avalanches with well defined edges were seen on steep slopes in the Seattle Ridge alpine as of 3 PM. Runout from a larger avalanche (~D2) was also seen in a larger gully on Seattle Ridge across from Sunburst. The angle was tough for this one from the side - see photo below - but it looked to be a loose snow avalanche that may have also triggered a section of slab within the gully feature.

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

Intense snowfall - ~2" per hour! - at the parking lot at 11 AM, with 12" of new snow overnight.
Snowfall rate slowed by 11:30, with ~3" falling between 11 AM - 3:30 PM when we left.
Obscured skies, with occasional patches of blue overhead.
The sun cast a shadow nearly half the time, even during periods of snow.
Light NW winds occasionally gusting moderate above 1700'

Snow surface

In the morning, a dry snow surface was observed at the parking lot, but things warmed up throughout the day. By 3:30 PM, 6" of moist snow was present on the surface at treeline, and the 20" of new snow from 3/29 - 4/1 was moist at the parking lot.


Numerous quick hand shear tests along the route. The slab was ~50cm thick in areas without wind affect, comprised of new snow over the past week, sitting on top of a melt freeze crust to treeline.

The slab was not cohesive below 1500' and would break apart before any failure with hard force. Between 1750' - 2200' this was also often the case, but on a few occasions a cohesive soft slab would fail with just easy force. The failure would take place at the base of the weekend's storm snow, just above a refrozen melt layer from last week. This melt layer showed signs of faceting in a snowpit (see below), with the location chosen just above 2000' where a melt layer was present on the surface but it had refrozen by today. Below 1500' a thin melt freeze crust capped moist to wet melt forms, still not frozen after last week's warmup.

Finally, above 1700', winds had moved recent snow around some, with 1-2.5' of new snow over the crust though no obvious wind slabs were encountered below treeline. See pit information below, including compression tests that failed with a lot of pop in buried surface hoar 2.5' from the surface. An ECT did not fail at that location, but on extended overdrive the block did fail and slide with gusto into the pit itself!

Photos & Video
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