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Avalanche: Turnagain

Location: Eddies

Date:
Observer:
Route & General Observations

Toured up standard Eddie’s skin track to a high point of 2500′. Looking at the distribution and reactivity of the 1/21 Buried Surface Hoar (MLK Jr BSH) layer within different elevation bands on the non-motorized side.

We intentionally dug a pit along the ridge looking for a thinner area where the MLK BSH would we closer to the surface. Upon descent we remote triggered a hard slab avalanche on the SW face of Eddies from the ridge. We were spaced about 5-10′ apart and bouncing ┬áto get a little speed. A group just below us on the ridge watched the avalanche release as we descended. No one was near it or caught.

Prior to this avalanche a skier descended the steeper SW face above without incident. We also noticed fresh debris in valley bottom directly below this area, but could not see any crowns due to the off-angle view and steep terrain below.

 

Avalanche Details
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Trigger SkierAvalanche Type Hard Slab
Aspect SouthwestElevation 2500ft
Slope AngleunknownCrown Depth2ft
WidthunknownVertical Rununknown
Avalanche Details

HS-ASr-R2-D2-O
A hard slab avalanche triggered remotely by a skier on the ridge and broke on the MLK Jr BSH.

The slab was relatively soft on top going to pencil hard snow on the bottom of the slab.

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

Fresh debris at valley bottom of SW face, further up valley from our turnaround point
Remote triggered avalanche on SW face

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

Low 20s
Clear-Few Sky above 2000'
Valley Fog between 1500-2000', dropping throughout the day
No Precip
Calm Wind

Snow surface

Road to ~1200'- Supportable crust becoming a crust/facet sandwich under 3-6" softer snow
~1500' -crust/facet sandwich becomes a thin crust under soft snow, but can still feel with ski pole ~12" below surface
~2000'- 2500'- 8-10" Soft settled snow showing signs of riming on surface.
~2500'- 10" Soft settled snow

Snowpack

The MLK Jr Day (1/21) BSH layer was found in test pits dug between 2000' and 2500'. In both pits it showed collapse but generally low propagation propensity. While these pits showed low propagation propensity, we were able to remote trigger an avalanche on a shallow flat ridge, showing the reactivity is still there in shallow connected spots.

Beginning at 1200' we had failure on isolation in hand pits on a crust facet sandwich 6" down.
~1500' the crust facet sandwich becomes very thin, but still getting failure with moderate force on a planar fashion 6" down

~2000' we found the MLK Jr BSH (4-8mm) buried approx 70cm (28") down with knife hard melt freeze crust directly below it, and the 1/11 BSH buried approx 85cm (34") down. In stability tests we were able to get a collapse, but only able to get propagation with extra non-stand force applied (Stomp) CT25, ECTX, PST70/100 (end) down 70cm on MLK Jr BSH. The MLK buried surface hoar looked to be metamorphosing into cupped facet shapes, possibly melt-layer recrystallization. See photo below. There were two additional melt freeze crusts (~1cm in size) down 50cm and 55cm, no reactivity on either layer.

~2500' we found the MLK Jr BSH (5-8mm) buried approx 12" down with pencil hard snow above and below it. In stability tests we were able to get a collapse, and a progressive propagation. CT19, CT16, ECTN16 & ECTN14 (Propagating at ECTN16)

Photos & Video
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