Southern San Juan

Avalanche

Justin Swantek · Jan 22, 2021 · Southern San Juan

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Weather

Calm, clear, perfect bluebird powder conditions during the day. At night, the low is in the single digits, accompanied by calm, clear skies.

Snowpack

As it stands on Friday, 1/22/2021, the E-N snowpack has two layers of concern. The first and more concerning of these layers is a buried layer roughly 50-90 cm down in the snowpack, likely from the dry spell in December. Every day since Monday (1/17), I have gotten whumps on this layer; with the addition of 6” (at 10,500’) on Tuesday (1/18), it became more reactive (ECTP13-22 x4), though this was not enough of a load to cause natural avalanches. However, I did cause a 400’ wide failure on a low angle treed slope, so there are large cohesive slabs to be found. As a general rule, slopes that previously had a wind slab from last week are now acting the same as non wind-loaded slopes in terms of test results; the wind slab has bonded well with the snow below and columns are failing on deeper layers (ECTP 20-30 x3), not the wind slab interface – this was not the case before the storm. That being said, the wind slab has not yet decomposed and has made for very variable riding conditions. The second layer of concern has yet to be buried. With the calm, clear nights, a layer of surface hoar (5-8 mm large) has grown on all shaded aspects. I found this surface hoar at all elevations from 9,500-11,200. If it does in fact snow 2’ this weekend (fingers crossed), it’s a layer that could potentially be a problem for storm slabs. For other aspects/elevations: SW-NW slopes at all elevations got nuked by the wind and only have the new snow from Tuesday, except in very isolated spots. SW-SE slopes NTL and ATL have layers of snow below the new snow, but have gotten blasted by the sun the past few days; this has caused naturals (they appear to be wet slides) that appear to have broken deeper than just the new snow (see pictures). SE-N slopes ATL have visible wind effects and likely have the poor snow structure described above; it will be interesting to see how it responds to the large load in this next storm!

Avalanche

The naturals mentioned above happened on Above Treeline, S/SE facing slopes. All in all, I saw 5 distinct crowns: 4 D1.5/R1 and 1 D1/R1.