Northern San Juan
AvalancheBecs Hodgetts · Dec 3, 2022 · Northern San Juan
Weather
Weather at 11 800' was calm, overcast, with the tops of surrounding peaks obscured. The rapid settlement of the new snow was easy to understand with the high RH and somewhat muggy feel to the day.
Snowpack
Northerlies near and below treeline have an HS range of 40 - 80cms. There is a basal facet layer 40cm thick. These striated facets are up to 3mm in size and fist hard. Notably (and cool), the early November dust layer is visible now as facets. The bottom of a 4F hard layer of decomposing fragments is the interface layer for failure in column tests and cracking on steep rollovers. The slab over this faceted layer makes up the other ~50% of the snowpack. This slab is soft (4F-F). ECT P13. Where the wind had drifted snow, the slight change in hardness from 4F to F is enough to propagate fractures approx 20-40 feet from the traveler. These conditions on slopes steeper than 35 degrees are touchy. However, the avalanche size should be small. The danger is when these small slides sweep you into terrain traps or solid objects such as trees or rocks. Above treeline, many slopes were stripped to the ground by recent strong southwest winds. Travis Lafferty noted in a recent observation that any northerly through easterly slopes that hold enough snow to recreate also have a strong over-weak snowpack structure. That is the case in this area.
Avalanche
Two small natural releases near treeline on a corss-loaded terrain feature.