Northern San Juan
AvalancheAnonymous · Nov 9, 2020 · Northern San Juan
Weather
Overcast to S1+; light winds, variable; temps in high 20s (est.);
Snowpack
NE aspect, ~ 11,500 feet; < 32 degree slope angle (mostly in 20s). Noted around 8-10" of 10-12% density (est.) snow from ground. Did not appear to be much else on ground, on the lower angle slopes, before Saturday's storm. An additional 6-8" lower density new snow fell overnight into Sunday. New snow was bonding well to Saturday's snow. Some localized drifting up to an additional 12" overnight. Observed no cracking, collapsing, or whumpfing along the approach, or on any lower angle slopes. Turning conditions good on supportable base.
Avalanche
On second lap, climbed an additional 20-30 feet higher along ridge, slope angle increasing into low 30s (est.), still no cracking or collapsing, snowpack remained the same as lower down. Heard a rumble (did not collapse where I was), and observed a med sized soft slab release on steeper, sheltered terrain above and to lookers right, about 50 feet away. This was on a different aspect and terrain feature from observer location. Crown wrapped around cliffs to lookers right, and ran into a deep gully below the subtle ridge line separating steeper and lower angled terrain. Slab pulled out to a near-ground bed surface, assumed to be the pre-Saturday snow, as it was up under steep northerly cliff band. Slab ran approx. 75' into gully and stopped on lower angled terrain. Not huge, but would be enough to get caught up and drug over ground & rocks, plus get buried in gully where it stopped. Also, not necessarily a close call today, but luckily the slab didn't wrap around further to the lookers left, which was above me, probably due to being a lower-angled bench than where it pulled out and propagated. In hindsight, staying to the lower angle slope just 20 feet lower would have been the better call. However, it was easy to go a little steeper given a lack of any observed weaknesses, prior to this slab.