Northern San Juan
SnowpackMatt Steen · Mar 5, 2013 · Northern San Juan
Weather
Rapidly warming day. Clear and sunny skies.
Snowpack
Traveled in Helitrax terrain. Previously seen skier traffic and explosive mitigation. Variable depths of snow above treeline. Exposed ridgelines and rocky prominences were scoured or left with little snow. Snow depths ranged from over 6 feet to less than 1 foot. Depth hoar was more pronounced around 12,000' (NW), but was evident and a little harder to trigger in instability tests near 13,000' (N). Soft slabs rested on these basal facets, though not any stiffer than 1 finger resistance. The upper portions of the snowpack were reactive in instability tests, but did not fail while skiing slopes less than 40 degrees. These snow pits confirmed the potential for shallow slides triggering deeper weakness within the snowpack and running near the ground. I would suspect where a stiffer slab exists, triggering an avalanche would be easier. Less cohesive slabs in these areas, and there is a lesser potential to trigger by either a skier or with explosives. Faceted-snow grains were evident on the snow surface at the lower (12,000'-NW) snow pit, not a good welcoming surface layer for this weekend's potential storm. While descending into treeline and below treeline terrain, the snow surface quickly transitioned to a slushy surface by 1pm, if not earlier on slopes that face the sun. Shady slopes remained cool and dry. A series of melt freeze crusts and weak faceted layers was primarily found below treeline on westerly trending aspects.