Southern San Juan

Avalanche

Chris Bilbrey Matt Huber · Nov 24, 2020 · Southern San Juan

Weather

Obscured skies and S2 at the start of our tour. By mid-day, skies broke and sun poked out for a pleasant afternoon with on and off snow showers. Low lying fog starting rolling over the pass in the later afternoon limiting visibility at times.

Snowpack

We found around two feet of new snow on northerly-facing slopes and settled snow depths on those slopes range from 3 to 4+ feet near treeline. Storm snow fell right-side-up with a layer of graupel 8 to 10 inches below the surface. This layer was not reactive in stability test. New snow fell on a myriad of old surfaces such as a melt-freeze crust and near-surface facets that most likely formed during our recent dry spell. We observed one isolated collapse on a west-facing slope with no shooting cracks. Our Extended Column Test (ECT) at the location of the collapse produced an ECTN 23 breaking at the top of crust. 4F-, faceted snow grains found below the crust. Traveling on northwest, north, and northeast-facing slopes didn't yield any signs of unstable snow such as collapsing or cracking. Storm snow was supportable to skis and boot penetration did not break through the storm layer. However, an ECT on a northeast-facing slope produced propagating results (ECTP 16 & 21) at the storm snow interface and near-surface facet layer (0.5-1.0 mm). The overlying slab was F to 1F- (top to bottom) and slide off column with ease. Despite not observing natural avalanches or having a lot of direct feedback from the snowpack, these test results highlight a concerning slab, weak layer structure in the upper snowpack. We felt that steep, northerly-facing slopes with a stiffer wind-drifted slab should be avoided or approached with extra caution.

Avalanche

We received a vague, second hand report of a snowmobile triggered slide south of Wolf Creek Pass. Limited information.