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

Weather:

• 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

Snowpack:

Cornice formation around treeline:

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: (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+):

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

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

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

Another view of crown propagation:

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