Northern San Juan
AvalancheAnonymous · Mar 1, 2022 · Northern San Juan
Weather
Sunny, 10-30 deg. F, light breeze. SSE aspect on peak 13,300. Started from 12,000 feet at about 8:45 AM. Summited at 11:40 AM. avalanche around 12,900 ft at 12:00 pm.
Snowpack
A Sun crust from the previous day’s warming was noticeable on southern aspects at about 12,000 ft. , and Eastern aspects had dry snow without a crust. A group of 3 had skied multiple wide SSE lines from this and two other adjacent peaks the previous day and told us that they had “arrived too late” at noon, which we took to mean that the snow was too warm when they skied. This being the second clear day in a row of strong solar insulation on the slope, And also given that there was clearly reduced snow due to wind and prior melting on the Southern aspects , in our minds the facts aligned to signal spring-type strengthening of the snowpack and a thin (approx 24-36 inches) snowpack. This was a false assumption and the avalanche was a dry slab consisting of low density snow on the lower half and a partially melted and refrozen crust layer on the upper half. Some melting had occurred the previous day but clearly not to the level needed to create the type of stability seen in the freeze thaw cycles of spring.
Avalanche
There was an upper ~250 ft. descent at a slope angle of approx. 35 deg. Which we all skied one at a time and gathered in a place in some rocks mid-slope that felt protected. Then one skier descended the larger, steeper slope, moving onto the more south-facing aspect gradually and stopping at the edge of snow near the skin track up on skiers left. The second skier followed and made 4-5 turns before triggering a large avalanche. A vertical fracture directly under the skier propagated approximately 150 feet above the skier and some distance below. The horizontal crown was approx. 150 ft across and 1.5-2 ft deep. The skier felt the snow move beneath them but was immediately able to exit the avalanche diagonally and move to the perimeter rocks. The three remaining skiers were unaffected and decided to down climb through rocks and thin snow to the lower skiers.