Northern San Juan

Snowpack

Bill Nalli · Feb 1, 2020 · Northern San Juan

Weather

Mild temps but slight breeze and cloud cover kept daytime highs lower. Snow surface stayed dry.

Snowpack

Mission today was to map out snow depths and wind slab distribution in multiple aspects and elevations. Near and below treeline, east through north have 80 to 120 cm HS. This zone has also taken a turn for the weak. Overall shallow depths (less than 120cm) has turned into small to large faceted grains. In some locations I am now finding advanced facets all the way to the ground. See photos of shallow and weak snow. Where the pack is less than one meter deep we have the weakest snow. Advanced cup-shaped, chained facets will not be able to hold much new load and will likely see avalanches with the first new inch of SWE. Much variability exist however and there is a mix of conditions at the surface from fist hard facets to a 1 finger thin wind crust above facets to a pencil hard wind slab above those same weak facets. The latter is the most concerning as this wind slab will likely hold a larger load before is slides and may propagate wider. As you move higher into the alpine, the wind has damaged much more of the terrain and very strong, dense slabs and scouring exist. Occasionally the wind slab is weak enough that the weight of a person is enough to make it fail. I found one spot on a cross loaded slope below a cliff band near treeline that collapsed as I walked into it. The weak layer was very weak, near surface faceted crystals.