Northern San Juan
AvalancheChris Bilbrey · Dec 17, 2022 · Northern San Juan
Weather
Chilly morning. Single-digit temperatures in the valley to start, but moderated into the low 20s above 11,000 feet under sunny skies. A light breeze was felt below the treeline increasing to moderate speeds along ridge tops.
Snowpack
Snow depths and overall coverage is still thin below 10,000 feet. As we climbed higher in elevation, slab depths above the drought layer facets ranged from 16 to 24 inches on northerly and east-facing slopes. Cracking and collapsing was most prevalent near wind-drifted pillows and areas directly below ridges near the treeline. Signs of unstable snow below treeline were almost absent, but observed in open areas prone to drifting. Stability test point toward a more stubborn slab/ weak layer combination with moderate force required to produce failures in Compression and Extended Column Tests. However, failure planes were clean and the block popped off weaker snow below quickly. Southerly aspects in the Rico Mountains are thin and snow coverage is fairly discontinuous. Crust are starting to form on south aspects and southeast aspects are still holding soft snow on the surface. Southeast-facing slopes near treeline have a concerning faceted crust structure below recent snowfall, but currently lack enough slab volume to pose much hazard. A quick pit on a southeast-facing slope yielded dirty (Q3) failures in Compression Test breaking in small, faceted grains below a 2 cm crust. We did not observe any signs of unstable snow on southerly aspects.
Avalanche
We saw numerous natural avalanches that most likely ran on 12/12 or during early morning hours of 12/13. These slides occurred on west through north to east aspects above 11,000 feet. While most slides failed in old, faceted snow near the ground, most avalanches did not break wide across terrain features as observed in other parts of the San Juan Mountains. This may be a product of how narrowly distributed early-season snow was in the Rico Mountains compared to other areas.