Rumbling collapses

CBAC CBAC Observations

Date of Observation: 12/13/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Various aspects near Kebler Pass and Lake Irwin.

Observed avalanche activity: Yes
Avalanches: Nothing new. Documented a few older slides from the past cycle.
Weather: Few clouds. Moderate southwest winds at ridgetop with some light transport at times.
Snowpack: Primary goal today was to test the sensitivity of the persistent slab problem on shady aspects. Although it’s getting harder to produce signs of instability than earlier this week, the snowpack is still talking. I skinned over, then jumped with skis on, and then post-holed into four suspect low-angle slopes below treeline. One slope remained quiet, one produced a localized collapse when I skinned over a shallow, wind eroded feature, and two of them produced rumbling collapses after I stepped out of skis and sunk my boot into the weak layer. Slab depths in this area were 75 to 80 cm to the 12/6 facet layer.
Also dug into a southerly aspect near treeline to test bonding to the 12/6 crust. No alarming results and no signs of instability while traveling on southerly aspects.

Surface hoar growth observed below treeline.