Northern San Juan
SnowpackBen Pritchett · Mar 4, 2012 · Gunnison
Weather
Light to Moderate North winds transported Moderate snow at ridgelines through the morning into the early afternoon; Light drifting near treeline. Sun triggered pinwheels in steep sunny terrain by late afternoon.
Snowpack
Height of snow varied 60-160cm. 2 PST results intentionally dug in strong snow areas both produced propagation likely scenarios on the basal depth hoar layers. PST 20/105 (End) dug on SE aspect (11,200') in a weak layer of basal facets that contained numerous percolation tubes. Crack propagated right through the percolation tubes. PST 40/120 (End) dug on E aspect (11,500') on a slope that received a huge amount of skier traffic (across from the Addie-S hut) over the course of the season. Tracks were plainly visible in the slab above the drought surface interface. 7 collapses observed between the two field groups on N-E-SE aspects. Some of these propagated on crust/facet combinations on sunny slopes, others on the depth hoar, and one below the recent storm snow drifted into a 45cm thick 4-finger to 1-finger stiff wind slab on 1mm facets. This wind slab collapse was triggered in the flats from below a small convex bowl w/ cracks propagating around 200' away, but no avalanche release. Snow surfaces were covered with small near surface facets on all aspects in the elevations observed (11,000'-11,700').