Observation: Public

Observation Details

Signs of Unstable Snow

Observations

Traveled from Anderson/Watson Snopark to Watson Lakes and the north side of Mt. Watson to document the recent avalanche cycle and investigate the 1/24 interface.

Above 4000ft, 100-120cm of recent snow from 01/24-02/02 brought HS to 4m+. Numerous large to very large natural avalanches ran 01/30-02/02, with crowns on all aspects. Many avalanches had impressive propagation (especially on S/W aspects of Bacon Peak, and the NW aspect of Mt. Watson). Several rounds of natural activity occurred during the cycle, and the depth of the avalanche crowns was variable. Some appeared to fail deeper on the 1/24 interface, but most were shallower. The vast majority of avalanches occurred on wind loaded upper elevation slopes. Large wet loose avalanches ran on 02/01 with rain to 5000ft. Most avalanche debris piles were covered by 1ft+ of low-density snow from 02/02. A round of solar triggered loose avalanches ran in steep, rocky, vegetated terrain today.

The 1/24 interface was consistently 90-110cm below the snow surface. Stability tests targeting 1/24 as well as inter-storm layers produced non-planar fractures (BRK) and no propagation. Below 5000ft, moist rounded grains (P) were well bonded to 1/24 which presented as a 10cm thick melt-freeze crust (K). Above 5000ft, the recent storm snow was noticeably drier and less dense, but also well bonded to 1/24. Inter-storm layers were settling quickly and gaining strength. Despite a lack of concerning snowpack structure and favorable test results in a handful of pits today, our group chose terrain less than 30 degrees away from overhead hazard. We are still only 24 hours out from a heavy loading event, and reports of surprising avalanches failing on weak snow associated with the variable 1/24 interface were on our minds the entire day.