March 18, 2015

Public Observations: Glen Alps

The following observations regard the same avalanche that occurred on the Powerline Pass (northerly) side of Flattop, below the saddle, Wednesday afternoon.  The first observation is from the party that triggered the avalanche, and the second observation is from another witness.

From the triggering party:

Remotely triggered a 1 meter thick 100m by 30m hard windslab on a cross-loaded gully sidewall, NNE aspect at ~2500′. Slope may have been as steep as 30-35 degrees, but most of the bed surface was 25-30 degrees.  The fracture must have propagated from us, traveled ~300 feet away where the slope angle looked to have increased to ~35 degreess, failed at the steep spot, and pulled back all the way to us at 25 degrees.

80cm of wind slab above 20cm of basal facets.  ECTP21 on the basal facets next to slab before it released.

Cloudy and windy weather, with wind loading.

From another witness:

Observed three skiers digging a pit at the bottom of a small cross-loaded slope when almost the entire slope avalanched.  It looked like about 60 or 70 yards wide and ran maybe 20 or 30 yards until where the slope flattened out.  Crown appeared to be two feet.  They tried to run out of the way but it looked like a couple of them got knocked off their feet.  Everyone appeared to be OK afterwards.

Photo of the avalanche:Avalanche on the north side of Flattop, Chugach Front Mountains, Alaska.


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