Northern San Juan

Avalanche

Jeremy Yanko · Mar 26, 2022 · Northern San Juan

Weather

Plenty warm with a steady breeze from the west helping to moderate the ambient temperature.

Snowpack

A weak freeze was noticeable upon poking up a predominantly east-facing route. WX stations in proximity showed 5 hours of below freezing temps around 11k and a 10 hour freeze closer to 12,000ft overnight. Our intent was to see how conditions worsened along the same route between 10,500ft and 12,400ft during the 9am to 2pm time frame. Below 11k on the way up. warm-moist surfaces and grains below were supportable to skis but not boot penetration as one could easily drive a leg well into the snowpack on shaded E/NE terrain. Hasty pits and small column snowpack tests revealed easy scores/isolation failures below partially re-frozen crusts with dust on top of moist rounding facets in the top 15-30cm of the profile. The 90cm snowpack here was comprised of moist grains to the ground. On the way out, ski supportability had decreased, providing "trap door" conditions by 2pm below 11k. Working through a steep rock band we decided to gauge the stability with a ski cut/stomp that gave way to a 2ft deep slab failing on mid-pack facets. The slide was small but enough to push you into trees. Closer to 11k and up to treeline the upper melt-freeze crust below 10cm of moist grains was substantially more supportable to boot penetration and remained that way upon the exit 3 hours later. We did notice that the crust was thicker (10cm) and preferred for both up/down travel with a southerly-tilt from east rather than to the north where the crust is less developed. In the alpine, the winds had left a good mark on the surfaces; eroding and hardening a lot of aspects. However some of the wind-slabs and sastrugi are softening at a quick rate. On due East around 12,500ft, psuedo corn skiing is taking shape via a stout 5cm melt-freeze crust.

Avalanche

Intentionally triggered to evaluate sensitivity to skier trigger.