February 27, 2016

Avalanche Investigation

South Fork Eagle River: Harp Mountain – 2 Bowls

Red flags (obvious signs of instability):

  • Large human triggered persistent slab avalanche from Thursday night (HS-ASu-D2.5-R3-O)
  • Wind slab shooting cracks
  • Subtle collapsing
  • Active wind loading


  • Cloudy to obscured skies with intermittent light snowfall, moderate to strong easterly wind, and temps in the mid 20s

Surface conditions:

  • Generally supportable wind slab with at least a dusting of fresh, moist snow


Cornice formation around treeline:2 bowls treeline cornice

Lower snowpit at 3192′, 257 degree W aspect, 32 degree slope, 138cm height of snow, ECTX, CT10 resistant planar down 21cm (ECT failure here as well, but beyond the standard test parameters) P-1F+ wind slab failing at density change:2 bowls lower pit (red lines showing avalanche path):

Snowpit on skier’s right side of crown 2/25/16 HS-ASu-D2.5-R3-O avalanche that caught and carried 1 skier ~1000′ and killed a dog, 4381′, 313 degree NW aspect, 37 degree slope, 109cm height of snow (note that this is on a thin side of the crown and in some places the crown itself is 150cm+):2 bowls crown profile

Screen Shot 2016-02-27 at 8.52.58 PM

ECTP23 sudden collapse down 54cm on 4F facets below crust (failure plane of human triggered avalanche):2 bowls ECTP

The crust at the bottom of the persistent slab with 4F facets below (persistent weak layer responsible for 2/25/16 avalanche accident):2 bowls avalanche pwl

CTV down 107cm on facet chains and depth hoar at the ground:2 bowls CTV 2 bowls facet chains

Another view of crown propagation:2 bowls crown

Toe of debris (house within 100 yards and out of view road within 20-30 yards):2 bowls debris toe