Southern San Juan
AvalancheChris Bilbrey · Jan 6, 2021 · Southern San Juan
Weather
Warm day with abundant sunshine and moderate northwest winds along ridge tops and in alpine.
Snowpack
The snowpack is much shallower on this side of the river valley as compared to slopes on the western side. Lots of vegetation poking through the snow surface on northwest aspects all the way up to about 10,800 feet. Below that, slopes are un-rideable and travel was restricted to snow covered mining road. As we climbed higher, snow depths increased but not my much - snow depth on west, northwest and north aspects was generally less than a meter deep. Strong northwest winds recently have scoured many areas directly below ridgelines and in upper elevation start zones. A similar theme exist, snowfall over the last month sitting above weak facets. Buried facets on a west aspect near treeline, however, are showing signs of rounding and ECTs failed to produce propagating results in multiple test. The slight turn to the north made all the difference and that same facet layer on a northwest aspect at the same elevation are much weaker and the layer is between 4F- and F. When crossing across a 30 degrees northwest facing slope, we observed a loud collapse and shooting cracks. Digging down, we found 20 cm's of 2 to 3 mm facets sitting on top of a 1F layer and below a cohesive slab with stiffer, wind-drifted layers near the surface.
Avalanche
We observed a natural avalanche on a southeast aspect around 1:15 pm today. Slide originated below a steep, rocky section of the ridge and at treeline. Our best guess is that loose snow sluffed from daytime heating and triggered a larger slide while moving down hill.