Southern San Juan

Avalanche

Chris Bilbrey · Mar 1, 2022 · Southern San Juan

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Weather

Warm and generally calm wind - subtle breeze along ridge tops. First day all season I drank all the water in my pack.

Snowpack

Melt-water continues to work its way further down in the snowpack. In an east-southeast snowpit dug below treeline, water had pooled above weak facets at a firm melt-freeze crust. Once the water passes through the crust, this could be a wet slab concern with additional warming. Northerly aspects near and below treeline remain the bulls-eye aspects/ elevations to trigger a large, dangerous avalanche. We observed numerous loud, audible collapses and easy failures in both Compression Test and Extended Column Test in F hard facets below the recent storm slab. In one instance, we observed a collapse on a northwest slope while traveling back up after descending the slope. On similar aspects above treeline, the recent storm slab was unreactive in test where it rest above a hard wind-layer or crust. The complexity here is that above treeline terrain harbored the most variability in old snow surfaces. You may encounter isolated areas where weak facets rest below the upper slab versus a hard layer with potentially different behavior at the new/ old interface. While traversing a low-angle (less than 30 degree) south to southwest-facing slope near treeline around 3:30 pm, we observed slope wide cracking - some en echelon cracks observed several hundred feet down the slope. If this was a steeper slope, it probably would have slid. The crust below was around 10 cm thick, but the upper half fully saturated making it look like melting ice on a lake. Below treeline due south slopes felt trap-door and additional warming could increase the odds to get wet, sloppy snow to move downhill.

Avalanche

Lots of avalanche activity visible from our last storm cycle along this portion of the 550 corridor once you get up in elevation above the highway. Most activity confined to N-E-SE aspects near and above treeline. In addition, a handful of Loose Wet avalanches above treeline on SE-S-SW aspects.