Southern San Juan

Avalanche

Chris Bilbrey · Jan 25, 2021 · Southern San Juan

Weather

Partly cloudy skies in the morning gave way to overcast skies then obscured skies and snowfall around Noon. Snowfall was steady for the remainder of the afternoon with an additional 1-2 inches accumulating. Winds were light below treeline and along ridges, but sounded slightly stronger higher up.

Snowpack

The La Plata Mountains are receiving some much needed snowfall. Since January 19th, we estimate that around 12 to 16 inches has fallen in the main valley floor, around 2 feet at 10,000 feet, and close to 3 feet around 11,000 feet and higher. This is all sitting above a snowpack that was previously thin and very weak. The new load is allowing Extended Column Test to again, produce propagating results with around 20 taps - blocks fully sliding off isolated column. We did not observe propagating results within storm layers in our test, but we did observe lots of natural cracking and sluffing in steeper terrain on slopes facing north through east to southeast. In addition, we were able to trigger a small soft slab on a southeast aspect while cutting across the top of the slope. As we climbed toward treeline, surface slabs were getting stiffer but drifting was not the extent as originally anticipated. At elevations around 10,000 feet and lower, the new snow is winning the battle and more new snow now sits on the ground compared to old snow that persisted over the past two months.

Avalanche

Although we didn't observe lots of signs of unstable snow, the monsters in the closet still reared their ugly head today. We triggered a large avalanche on an east-facing slope below treeline that broke in a thick layer of facets (4F) below all of January snow. The slide failed when a rider came to a hard stop on a flat spot above a steep convexity (>35 degrees) and the slide broke at their skis.