Avalanche: Hatcher Pass

Location: 4068 Obs and Avalanche on Arkose Ridge

Date:
Observer:
Caleb Rauch
Route & General Observations

APU Snow Science 1 field day, looking for evidence of persistent slab problems. We planned to tour to the ridge of 4068, but found numerous signs of instability and opted to stop and dig pits on the east facing bench at 2750′.

Surprisingly few riders out for a bluebird Friday.

Avalanche Details
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Trigger SkierRemote Trigger No
Avalanche Type UnknownAspect West
ElevationunknownSlope Angleunknown
Crown DepthunknownWidthunknown
Vertical Rununknown  
Avalanche Details

Witnessed a large, remote skier triggered slide at 2:35 pm; on the ridge east of the road.

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)?Yes
Cracking (Shooting cracks)?Yes
Observer Comments

Multiple occurrences of shooting cracks and whumphing on slopes steeper than 30 degrees. Cracks were remote in some instances, and propagated tens of meters. Observed several recent avalanches, ranging from small to large on a variety of aspects.

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

Sunny and clear skies with calm wind and no precip. Temperature was 28.4F at parking lot, and 23 at our high point of 2750'.

Snow surface

15 cm of soft snow made for enjoyable riding conditions. We did not encounter any wind-affected snow, but saw evidence of wind events near ridgetops. A sun crust was present just below the surface on solar aspects, and sun was softening this snow by our return to the trailhead at 3pm.

Snowpack

We dug 5 west facing pits at 2750'. Snowpack height varied from 110 to 200 cm.

Our layer of concern was 4 cm of facets above a drizzle crust sandwich, around 45 cm down. Stability tests produced several relevant results at this layer:
ECTP11 x2
ECTP13
PST35/100END
PST40/100END
PST45/100END
This layer was unreactive in half of the pits and produced no results.
Notably, the bottom of the snowpack featured 35 cm of advanced facets/depth hoar.

Overall, the snowpack had moderate strength and moderate to high propagation propensity.

Photos & Video
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Powder cloud from skier triggered avalanche across the valley. Crown visible on peak in center left of image.  

Location
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