Northern San Juan
AvalancheColin Mitchell · Mar 20, 2021 · Northern San Juan
Weather
Another warm day with high thin clouds. Winds picked up mid-morning and were mixing down to below treeline, helping to keep the snow cool.
Snowpack
I visited the Brooklyns and Red Mountain Pass study plots. The Brooklyns had an average HS of ~120 cm. The surface was a crust layer that was breaking down in the morning sun. Water has penetrated about 65 cm into the snowpack here over the past few days. These upper layers were a jumble of perc columns, ice masses and moist-to-wet rounding facets. Below this was dry rounding facets and depth hoar 1f to P hard. Water hasn't yet reached the depth hoar at the bottom of the snowpack. Cooler temperatures overnight and tomorrow should lock up upper layers and put the brakes on melting for now. The snowpack at the Red Mountain Pass plot is still gaining depth. The average HS is around 170 cm. Sun and temperature effects were much less pronounced in this lightly gladed, low angle area at 11,000'. Overall a deep, relatively solid snowpack of rounds and rounding facets with a couple of melt-freeze crusts in the upper half. Water has only penetrated a few centimeters into the snowpack. I found a thin layer of rounding facets in the midpack which produced a non-propagating fracture with an ECT, ECTN24. I tested the rounding depth hoar near the ground with deep tap tests, and got moderate results.
Avalanche
No new avalanche activity observed today. Lots of rollerballs and surface sluffing a few inches deep up to about 11,000' from yesterday afternoon.