AIARE 2 Avy Course

CB Avalanche Center2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/11/2017
Name: Donny Roth
Subject: AIARE 2 Avy Course
Aspect: North, South, South West, West, North West
Elevation: 8,900’ to 9,900

Avalanches: On our descent, on a SW aspect at 9,300’ I intentionally ski cut a small convexity and managed produce a D1-R1 soft slab avalanche that ran on the crust. The crown was 15-cm deep, about 10-meters wide and started on a slope we measured at 43º. It ran about 50-meters down a 35º slope and the debris stopped at an aspen grove. We proceeded to attempt to duplicate this and got a few smaller results on slopes over 40º, but could not get anything to go on slopes in the 30s.
Weather: Broken skies with a period of high thin clouds and strong solar radiation. Light snow, starting at about 1430, no significant accumulation. Calm to light, SW winds. High temp of 0ºC recorded at 9,500’ at 1300.
Snowpack: New snow had settled to between 15 and 20 cm. We measured 30cm of new in this zone the previous day and estimated an HN24 of about 8cm, so settlement was obvious. Snow on solar aspects was becoming moist quickly in the afternoon. On S-SW aspects the new snow is on top of a 2cm, 1F melt-freeze crust. SH was evident on all aspects. A series of small column tests produced easy results on a SW aspect at 9,580’. CTE (4) SC @ the 1/19 SH later 17cm down. This same layer produced an ECTP (1) that propagated across the column. On the north aspect at this same elevation, the small column tests were similar and we got a PST (70/100) End. In both cases the above slab was still a soft slab, but the southwest aspect was moist snow.