Northern San Juan
AvalancheJeff Davis Ann Mellick · Jan 2, 2020 · Northern San Juan
Weather
Cold, clear, and windy above treeline. Winds were light near and below treeline even on exposed ridges.
Snowpack
What a change 36 hours can make. The most recent storm produced 9.5" of new snow with 0.6" SWE on Red Mountain Pass. Strong northwest and north winds drifted the new snow onto leeward slopes. Banners were observed off high mountain peaks, but the winds were much lighter near-treeline. Digging on a southeast facing slope at 11,800' we found that the new snow was not bonding well to the preexisting crust (old snow surface). The snow failed and propagated easily at this interface. Digging deeper, we found a number of crust/facet combs along with a firm mid-pack. All this sitting above rounding moist depth hoar and facets and a hard basal crust, where we got hard propagating failures. The area we dug was around a meter and a half deep, but only a few meters to either side the snowpack depth was much shallower. The south side of the compass is currently the bullseye for avalanche activity. A layer cake of crust/facet combos topped by recent wind loading has made this aspect particularly volatile. Small aspect changes as well as changing loading patterns over the past weeks have increased the spacial variability and complexity of our evolving winter snowpack.
Avalanche
We observed multiple Storm Slab avalanches on south and southeast facing slopes. Other observers reported Loose avalanche activity on east to south through west facing slopes, but slab avalanches specific to southerly's.