Southern San Juan

Avalanche

Chris Bilbrey · Nov 10, 2020 · Southern San Juan

Weather

Frigid temperatures to start. 10F in canyon bottom and 4F at 10,000 feet. Otherwise, clear skies with temperatures climbing into upper 20s. Ridge top winds producing snow plumes but otherwise, winds were negligent below treeline.

Snowpack

Snow depth and overall snow cover is thin below 10,000 feet. Above that, snow depth increases dramatically. We found 2 to 3 feet of snow from our most recent storm above 11,000 feet with deepest accumulations on northerly aspects and on the leeward side of terrain features. Unfortunately, those are the same spots where we found a layer of 2 to 3 mm facets to be the thickest. This persistent weak layer is what's left from the late-October storm. This layer varied in distribution across slopes we traveled and is found on northwest, north, and northeast aspects near and above treeline. Slopes facing east through south to west did not have this layer or slopes below about 11,000 feet. We did not observe any signs of unstable snow like cracking or collapsing. However, our Extended Column Test (ECT) produced propagating results (ECTP 22 and 21) where the layer of facets exists. All aspects below 11,000 feet had a 1 cm rain crust with faceting above and below. We estimate this crust to have formed between 11/7-11/8. At the present, the slab overlying the faceted crust was not reactive and did not produce propagating test results in ECTs. Throughout the day, we observed a lot of drifting in the alpine leaving some areas scoured with adjacent slopes being loaded.

Avalanche

None observed.