Northern San Juan

Avalanche

Jeremy Yanko · Feb 23, 2022 · Northern San Juan

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Weather

Off and on S1 rates through much of the outing. Winds calmed and snowfall intensified to S2 around 2pm.

Snowpack

Height of new snow accumulated since 2/21 ranging from 40cm to 65cm around 10k-11,200 with ridge drifts measuring up to 100cm. Big wind loads on this easterly ridgeline felt hollow underfoot and probed as such too. An upside down heavily wind-pressed 4f- slab caps off the top 30cm of a fist hardness storm slab below. Depths and slab conditions varied along this mostly cross loaded ridgeline. It was fairly impressive to see the amount of wind effected snow below treeline, yet this area is rather exposed to the prevailing canyon winds. Cracking and collapsing was abundant on nearly any slope that has a northerly tilt to it where a thin faceted crust or near surface facets reside at the interface of the new storm slab. An even dust layer near the old interface was found here alike many locations in the San Juan's.Fair stability w/ out collapsing and high snowpack test scores was observed on due east and southeast BTL. Some S/SE start zones NTL were stripped down to the previously formed melt-freeze crust.

Avalanche

Several creek bank "slips" D1 or less slides and arresting fractures could be seen along County Road 110 over a 5 mile drive. Most were northerly though both one on east and west off of steep slopes were observed. Westerly may have been triggered by road crew plowing. Two significant and separate debris piles estimated to be D2's culminated in the same drainage of Fairview Gulch. One slide appeared to have initiated out of a steep loaded NE ridge and ran on a predominantly East facing crust. Two smaller D1.5 avalanches were observed along a E/NE ridge. One was a natural storm slab on Ptarmigan point (NE @ ~11,500) failing on a faceted crust. Second one was a stubborn remote trigger provoked by a "3rd loading step" on a wind loaded ridge NTL (N/NE ~11,850) failing on a similar 1f- faceted temperature crust on top of near surface facets.