Northern San Juan
AvalancheColin Mitchell · Feb 11, 2021 · Northern San Juan
Weather
Warm day with lots of radiation. Winds were light at my field site. Some light wind transport and flagging on the neighboring peaks that seemed to tail off in the afternoon.
Snowpack
I traveled north-facing slopes below treeline and south and southeast aspects right at the below treeline/near treeline transition, ~11,400'. North-facing slopes had an average HS of 140 cm. The snowpack consisted of a stout slab 50-70 cm thick over facets with about 8 cm of new snow on top. The facets became weaker, and the strong-over-weak layering more pronounced as I gained elevation. Snowpack tests on an open slope at 11,400' produced hard, propagating results on rounding facets 56 cm down. ECTP 23 & 28. On southerly aspects the HS averaged around a meter. The radiation was intense by midday, and the recent snow was moist and had consolidated to 5 cm. The upper half of the snowpack was about 50 cm of rounding facets and old crusts that stiffened from 4f to P hard with depth. Below 50 cm, the snowpack consisted of 4f and F-hard rounding depth hoar with a refrozen K-hard layer of facets at the ground. ECT's produced propagating results on the depth hoar layer, ECTP 22 & 27. The snowpack here was supportable to skis, but boot pen was 85 cm (ground). As I climbed into my skis after my profile, I initiated a rather large collapse, maybe 100' in diameter.
Avalanche
Many old crowns from late January were still visible in the north-facing trees in Porphyry Gulch. No new activity observed other than some rollerballs in the Eagle down near the highway.