Avalanche: Hatcher Pass

Location: Upper Willow Creek

Date:
Observer:
Anonymous
Route & General Observations

Palmer side > Upper Willow Creek

Contact, Location & General Observations
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Forecaster Comments

It is important to remind ourselves that we can trigger avalanches from well below slopes, even from the flats. Collapsing has been observed by numerous people, and it is the act of collapsing the snow, even in the flats, which can travel like a wave under the snowpack up steep slopes, triggering avalanches above. Sound form a snowmachine can not trigger avalanches, but may appear to if we do not understand the mechanics of snow failure. In this case it may have been a cornice failure that triggered the avalanche.

Avalanche Details
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Trigger NaturalRemote Trigger Unknown
Avalanche Type Cornice FallAspect Northwest
Elevation 4400ftSlope Angleunknown
Crown Depth 20inWidth 300ft
Vertical Run 500ft  
Avalanche Details

Observer reports a cornice failure triggering a slab avalanche.
No involvement, nobody caught.

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)?No
Observer Comments

This group felt a large collapse while sitting on their machines in the flats. This occured at a separate time from the avalanche, but is consistent with other reports. Collapsing is a bulls eye clue for ripe avalanche conditions.

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

Patches of clearing with clouds late in the day.

Snow surface

Moist, heavy new snow.

Photos & Video
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N,4400', Storm snow avalanche approximately 20" deep, Crown visible near ridgeline.  

Location
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