Northern San Juan
AvalancheAmy Pertuz · Dec 15, 2022 · Northern San Juan
Weather
Cold day with a start in the single digits and high temperatures in the teens. Very light snowfall throughout the day, with calm winds near and below tree line. The cold temperatures kept the snow low-density. This made for yet another day of very incremental loading with a few inches of new snow each day this week.
Snowpack
The snowpack is just starting to gain enough depth to provide reliable travel on westerly below tree line slopes in this area. The persistent slab problem was found here, but at lower elevations it is only beginning to connect across the terrain, and remains more isolated to deeper lenses of snow. Cracking and rumbling collapses were easy to provoke all day. Higher up in the below tree line band, the coverage became more connected and the collapses were occurring across a much larger area. The height of snow on below tree line westerly slopes here ranges from 60-90cm, averaging 70cm. Large, faceted grains make up the bottom half of the snowpack here, and the interface of interest is a faceting slab in the middle of the snowpack sitting above large, developed facets. This 1F- slab layer ranged from 6-8cm thick and provided just enough cohesive snow that travel was possible on skis here despite soft snow layers overall. Foot penetration was consistently to the ground. This thin midpack slab also provides just enough of a cohesive layer that collapses could communicate across such large areas. I would not expect this set up to hold much load, and it could become more sensitive as warm temperatures arrive and the surface slab settles and stiffens. CT and ECT tests both failed/propagated on 8 taps.
Avalanche
No avalanches seen today. Poor visibility into alpine.