Southern San Juan

Avalanche

Chris Bilbrey · Jan 17, 2020 · Southern San Juan

Weather

Windy sums it up! Periods of heavy snow (range from S1 to S2) along with blowing snow and howling winds created poor visibility and lots of wind-sculpting even below treeline. We did observe a couple short breaks in clouds that allowed the sun to pop out but otherwise, skies obscured all day. Temperatures were in the teens during the afternoon.

Snowpack

We found around 8 inches of new snow on wind-ward slopes and around 12 inches on leeward slopes near treeline - some drifts were up to two feet thick. Lots of wind-sculpting and wind-stiffened snow near and below treeline. Big whale humps of snow along ridgelines and in open, treed areas. Storm snow arrived denser than the previous two storms and you could feel the upside-down layering. It made for tough trail-breaking where deeper drifts formed. Isolated surface cracking while skinning uphill in drifted pockets and numerous audible collapses on southeast, south, southwest, west, and northwest-facing slopes near and below treeline. Surface cracking more prevalent where new snow fell onto a crust (sunny aspects) versus softer snow (shady aspects). We observed propagating test results in long-column test failing in wind-drifted snow on a northeast aspect (ECTP 11) and in two different persistent weak layers in the top meter of the snowpack on a northwest aspect (ECTP 13 & 18) - both near treeline. Although we found these concerning test results, we were unable to trigger avalanches or observe propagation on heavily wind-loaded, small test slopes. Poor visibility limited the opportunity to get eyes on many bigger, steeper terrain.

Avalanche

We observed cracking in the new snow on steeper convex test slopes facing south and southeast near and below treeline by the afternoon. None produced avalanches. We did not observe the same cracking with ski pressure on similar type slopes facing north to east.