Aspen

Avalanche

Colin Mitchell · Nov 22, 2014 · Aspen

Weather

Warm temps, calm winds and clear skies in the morning were starting to give way to cloudy skies by noon. Wind was picking up all morning, and was moderate from the WSW at the time of this observation. Some snow was starting to move around from about 11 AM onwards. Warm temps and lots of sun were beginning to melt snow on southerly aspects.

Snowpack

Average height of snow varied from 25-40 cm. Snow cover on South aspects was limited to snow from the 11.12-11.16 event, and showed no signs of instability. A 1-2 cm crust had formed on the surface in many of these sunny areas. On other aspects the snow surface was either 3-5 mm surface hoar or 1-2 cm near-surface facets. The surface hoar was quite widespread, and extended from the trailhead up to 10,700 ft and beyond, in any areas open to the sky. Last week's snow was well on the way to becoming all facets, but was still strong enough to form a 4F slab. This slab was not cohesive enough to propagate a large crack, but localized collapses were widespread on N aspects that still held old snow from earlier this month. The largest collapse was around 30 square meters. The snowpack on N facing slopes was about 40 cm deep with a 28 cm thick 4F slab sitting on top of 12 cm of F hard depth hoar. The slab was mostly composed of 1-2 cm facets and showed some bonding between the grains. The bottom layer was 2-3 mm depth hoar, showing some signs of rounding. The slab failed on the depth hoar layer during snowpack tests, ECTP 12 SC and ECTP 14 SC.