Northern San Juan
AvalancheColin Mitchell · Dec 4, 2019 · Northern San Juan
Weather
Partly cloudy skies, warm temperatures and very light winds.
Snowpack
The snowpack in this generally northwest-facing terrain consisted of a 40-50 cm thick 1-finger hard slab resting on depth hoar from October, and topped by 10-20 cm of softer snow near the surface. The snow surface varied from some crusts in sun-exposed areas, to 10 mm surface hoar and well-developed near-surface facets in shady and protected areas. Our first snowpack test was in the below-treeline band, on a slope above the road near a skier-triggered avalanche from Sunday. The profile clearly showed the weak depth hoar at the ground. An ECT test propagated with 11 taps, a moderate result. Descending from the profile site, we collapsed the entire slope. As we ascended, signs of instability increased. We triggered large, propagating collapses from the skin track every few minutes until we topped out at treeline. A profile here on a NW aspect showed a similar snowpack, although a little deeper. An earlier party had skied this slope and triggered multiple collapses and shooting cracks. An ECT test produced a propagating result with moderate force, 13 taps. We triggered another collapse during our descent which produced extensive cracking over a wide area. We traveled on terrain with a slope angle in the mid-20's. The collapses we experienced were large enough that they could have produced D2 avalanches in steeper terrain.
Avalanche
No new activity observed