Southern San Juan

Avalanche

Chris Bilbrey · Dec 8, 2020 · Southern San Juan

Weather

Mild, early-December day in the mountains. Temperatures were in the mid 20's F to start out and climbed into the upper 30's F by the late-afternoon.

Snowpack

Snow cover is barley holding on to below treeline northwest, north, and northeast-facing slopes. This is mainly above 10,500 feet and we traveled in street shoes on bare ground up to about that elevation. Below 10,000 feet, all aspects have either melted out or don't harbor enough snow cover to create a smooth sliding surface (lots of vegetation poking through). Slightly deeper snow depths are found near treeline on northerly-facing terrain. This elevation band will most likely be the most susceptible to producing widespread avalanching if we ever stack a slab above - full depth facets on many northerly, near treeline areas. We found less unconsolidated, weak snow surfaces in the alpine in this area as compared to other portions of the South San Juan. It appears the La Plata Mountains have received multiple periods of strong winds since mid-November forming stiff wind-drifted surfaces that range from 2 to 4 inches thick. Near-surface facet formation observed below the hard wind-board with 4 to 6 inches of 4F- facets lurking underneath. This stiff surface will help bridge larger, future loads before the bridge collapses. In sheltered, alpine areas we found 10 to 20 cm's of 4F- facets sitting above a 4F layer and 1F mid-pack. Ski pressure did not instigate loose snow sluffing and recent warm temperatures appear to have promoted additional settlement in surface facets helping them bond better to layering below. The caveat is these alpine areas with weak surfaces will not support the same future load as spots with a harder surface.

Avalanche

None Observed