Southern San Juan

Avalanche

Chris Bilbrey Mike Barney · Mar 22, 2021 · Southern San Juan

Weather

Light snow showers on and off until about 1:30 pm with around an inch of additional accumulation. Skies transitioned back and forth from overcast to a few clouds until about 3:00 pm. Around that time, winds shifted to the west, increased and moderate blowing snow noted along higher ridgelines and peaks.

Snowpack

We traveled on multiple aspects at all elevation bands (where there was snow - dry below treeline on southerly's) to evaluate drifting and slab formation at upper elevations. Snowfall accumulations overnight and this morning were negligible below about 10,500 feet. Above that, we found 4 to 5 inches of new snow with some drifts up to 12 inches thick in the alpine. We observed very light wind effect to the new snow, good bonding with various old snow layers, and no cracking in deeper drifts. We easily triggered small loose dry sluffs with ski pressure below ridgelines and on the backside of steeper convex rolls. Sluffing traveled farther where the new snow rest above a crust. As wind speeds increased in the afternoon, more efficient snow transport occurred onto northeast, east, and southeast-facing slopes in the alpine. Probing around we didn't feel any concerning dry snow weak layers near the surface at upper elevations and the lack of recent avalanche activity also suggest that deeper weak layers of concern appear less reactive now than earlier in the month. On southerly-facing slopes, the new snow quickly settled during breaks in the clouds, but snow surfaces remained mostly dry above treeline. The new snow on east through south to west-facing slopes near and below treeline started to get moist by the afternoon. Rollerballs from steep, rocky terrain below treeline were the only evidence we saw of wet snow activity. The snowpack below treeline on all aspects consist of moist grains top to bottom but cooler weather has locked up the snowpack for now.

Avalanche

We saw two fresh avalanches that most likely ran overnight or this morning. One was a small, shallow wind slab on an east aspect above treeline and the other was a small loose dry avalanche that failed below a large cornice on a northeast aspect. Both appear to be triggered from recent wind loading.