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Avalanche: Girdwood

Location: Notch Mtn

Date:
Observer:
Route & General Observations

Notch Mtn to Treeline (~2400′), then down a north aspect.

Avalanche Details
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Trigger SkierAvalanche Type Soft Slab
Aspect WestElevation 2400ft
Slope Angle 38degCrown Depth 3in
Width 100ftVertical Run 30ft
Avalanche Details

At the top of our route, as we started up a steeper rollover on a skin track that had been set yesterday, we managed to trigger a soft slab of today’s snow - 3” thick - that cracked and propagated ~100’. Portions of the rollover that were greater than 38 degrees slid, while cracks formed where the rollover was ~35-38 degrees. This occurred right after a quick pit (pictured below), where today’s snow and the snow from the end of last week - the bed surface - seemed of similar density and hardness. A shovel tilt test of the top 6” of the snowpack afterwards did clearly depict the density change, with the top 3” moving on the first light tap. Super interesting, as the slab was nearly too soft to even pick up with gloves, and the mere weight of the shovel would collapse the top layer into Friday’s snow on a standard CT!

See a few photos and a video of triggering a smaller rollover below!

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)?Yes
Observer Comments

See avalanche description above; after the first slide, it became apparent that any rollover steeper than 38 degrees would exhibit the same behavior, regardless of aspect, elevation, or potential for wind exposure.

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

Snow! Nearly an inch an hour throughout the day
(7" on truck at parking lot after 7 hour day)
Overcast or Obscured Skies
Calm with the occasional light easterly gust
Temps in the 20s

Snow surface

Ski penetration of 8-12" throughout the entire route. See snow structure photos below.

Snowpack

See photos below for snow structure and test results.

Photos & Video
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https://www.youtube.com/watch?v=nCCA59lrAXg&feature=youtu.be&fbclid=IwAR0ON4AOxkh8p83jhL9Basbhy4lWJfpV_EtDYbCEAaEHqDcrf7hEwuTyrwE