Northern San Juan
AvalancheJeff Dobronyi · Dec 14, 2014 · Northern San Juan
Weather
At treeline, 12,000', west aspect, time 1100. S1, sky obscured, winds light gusting to moderate, from the north. Temps below freezing, estimated 20 degrees F.
Snowpack
Informal snowpack obs below and at treeline showed a faceted deeper snowpack with 30cm new snow. No whumphing or hollow sounds, probably because there was no stiff slab in the snowpack. On SW aspects below and near treeline, a crust was observed beneath new snow, though this crust did not seem to be propagating any fractures. No whumphing observed, also this crust often did not support the weight of a skier descending (breakable). Steeper W and NW aspects showed poor bonding at the 12/13 storm interface. On these aspects, slopes over 35 degrees produced shooting cracks in the storm snow, up to 10 feet long. Despite widespread cracking, we were not able to trigger storm slab avalanches, though we skied uniform, supported slopes at or below 35 degrees. I suspect larger soft slab avalanches could run on steeper unsupported features, but where we chose to ski, the storm snow seemed too incohesive to produce large avalanches.
Avalanche
We triggered one avalanche, though I consider it not indicative of the larger avalanche danger because it was on a slope that had avalanched to the ground yesterday, Saturday, 12/13 in the presence of one of the members of our group. As such, the 20cm of snow that had fallen since noon yesterday on this slope fell onto bare ground, and seemingly did not bond well. We anticipated shallow and poor skiing on this slope, and our group decided to cross the slope at the old crown to access some trees on the other side. The first member to cross the slope triggered the avalanche, which again ran to the ground. Slope is located just south of Serpentine slide path, around 11,550', NW aspect.