Avalanche: Hatcher Pass

Location: Arkose Peak, North Ridge

Date:
Observer:
Route & General Observations

On January 7 a party of five skiers remotely triggered an avalanche in a nearby gully while ascending the north ridge of Arkose Peak on a westerly slope in Hatcher Pass (southeast of Lonesome mine). No skiers were caught.
Though we had no signs of instability on our approach, we were closely monitoring slope angles and were travelling on 30d or less slopes. On a broad slope to the right of a major gully, I skinned slightly closer to the gully than the others. Upon turning, I felt and heard a large whoomph and ‘rolling thunder’. We observed the lower third of the avalanche from our location. On the ski down the broad slope Elena and John reported shooting cracks. The day was mostly clear and calm with temperatures in the 20’s.
With closer inspection, the crown face was about 1’ with the right flank (climbers view) upwards of 3’ with two significant slabs. The crown face was at ~4,400’ and the runout zone at 3,600’. The debris was contained within the gully spread over about 300 yards and possibly 10’ deep or more.

Contact, Location & General Observations
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Forecaster Comments

A great example of the untrustworthy nature of buried persistent weak layers. Traveling in avalanche terrain will continue to require attention to safe travel techniques and preparedness for rescue in the chance that you are able to trigger an avalanche. Buried persistent weak layers will continue to be problematic throughout the season, although the likelihood of triggering this avalanche problem will vary between periods of varying sensitivity and activity.
Buried persistent weak layers will also continue to allow people to trigger avalanches from above, adjacent to, from below, and remotely (such as this avalanche).
While many recreators were able to ride a large variety of terrain without incident this weekend, this avalanche demonstrates that while likelihood is low, consequence is high enough to bury, injure or kill.

Avalanche Details
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Trigger SkierAvalanche Type Hard Slab
Aspect SouthwestElevation 4100ft
Slope Angle 30degCrown Depth 12in
Width 200ftVertical Rununknown
Red Flags
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Observer Comments

None until the avalanche.

Weather & Snow Characteristics
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Weather

Calm winds, mostly clear skies, shadowed terrain, mid 20's temperature.

Snow surface

2" of fresh dry snow over very hard non-breakable crust.

Snowpack

Not done.

Photos & Video
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