Northern San Juan
SnowpackMatt Steen · Dec 9, 2012 · Northern San Juan
Weather
Cold day. We started hiking by 9:30am. A cold inversion was in the valley, and temperatures rose as we ascended the route. Mostly snowy (S-1) ascent until noon when the clouds cleared for about a half an hour. Snow returned for another hour or so until 3:00pm. Moderate-ridgeline winds were out of the north by noon, redistributing storm snow on south-facing slopes. Clear skies and cold temperatures set in for the remainder of the evening. New snow accumulations were a measured 2 inches in the valley and 6 inches at treeline.
Snowpack
Shallow. We skinned from 9800 feet. We had to remove our skis for a few hundred vertical due to the shallow snowpack and downed timber. We measured 2 inches of storm snow in the valley. By the time we topped out at around 12,000 feet, storm snow measured 6 inches. Moderate northerly-ridgeline wind was redistributing storm snow onto southerly slopes. Overall, depth of snow measured between 1 to 1.5 feet. The base layers of the snowpack are cohesion-less facets on shady north-facing terrain. I did find a thin (3 to 4 inches) persistent slab. The slab was isolated on a northeast facing slope at treeline, within 100 feet of the exposed ridgeline. This slab was very reactive in snow-stability tests (CTV). A ski cut produced a fracture with no propagation. Elevations below this isolated-persistent slab, the snowpack returned to storm snow resting on weak cohesion-less facets.