Southern San Juan

Avalanche

Chris Bilbrey · Feb 3, 2020 · Southern San Juan

Weather

Just a pleasant day in the mountains. Snowfall started around mid-morning and continued all day. Precipitation intensity ranged from S1 up to S5 with new snow accumulations around 5 inches and drifts near treeline up to 10 inches thick. Strong southwest winds and extreme gusts (guessing some over 70 mph) produced lots of blowing snow and erratic wind loading on open slopes. We did not travel much above treeline as poor visibility made deciding up or down a challenge - widespread and deeper drifting expected in bigger, higher elevation terrain.

Snowpack

Southerly-facing terrain has developed a firm melt-freeze crust from previous day's warm temperatures and abundant sunshine. At mid and lower elevations, new snow was not deep enough to produce sluffing with ski pressure above this crust on steeper slopes, although this might change with continued snowfall overnight. Today's strong winds were efficient at distributing the low-density snow across the landscape. Effects of drifting and snow sculpting visible along treed ridge tops but quickly dissipated as we descended downslope. Near and above treeline, south and southeast-facing slopes were scoured down to the old snow surface with some areas benefiting from cross-loading, swirling winds, and erratic loading patterns. North to east-facing terrain harbored the deepest and most widespread drifting and this is where wind drifted slabs felt the thickest (4F to 1F). On an east-facing slope at treeline, buried near-surface facets produce propagating results in Extended Column Test while the same weak layer on a northeast-facing slope at a slightly lower elevation did not. We only observed cracking in isolated areas with thickest drifting but we also avoided slopes over 35 degrees that are open and prone to wind-loading at treeline. Minor and harmless sluffing observed in steep, north-facing trees from ski pressure that didn't travel far.

Avalanche

None observed today.