Northern San Juan
AvalancheChris Bilbrey · Dec 26, 2018 · Northern San Juan
Weather
Mix of sun and clouds with a light breeze along ridges. Intermittent snow showers later in the afternoon that didn't amount to any accumulation
Snowpack
Observed a few natural storm slab avalanches on various aspects and elevations. 12-20 inches of new snow in this portion of the North San Juan zone since 12/23. New storm slab was soft and primarily F to 4F (wind-drifted areas). We observed several whumpfing collapses and shooting cracks in terrain below ridges. Small test slopes produced mixed results with some producing no signs of unstable snow while others produced cracks in the storm slab but none moved down slope. ECTs produced mixed results on buried facets and ECTN results observed in multiple pits below storm slab. PSTs propagated to the end of the column within the first third on buried facets. Evidence of wind transport seen above treeline on open slopes.
Avalanche
The group in front of use triggered a SS AS R2 D2 on a northeast aspect below treeline in a prominent gully. The avalanche initially failed below the new storm slab and then stepped down to weak snow above the ground. It did not propagate across the gully and onto the northwest aspect of the gully. It ran approx. 500 vertical feet down to Prospect Gulch. We did not feel comfortable crossing the drainage to inspect the crown line. Our descent was along the treed rib above where the avalanche occurred and to the east.