Upper Cement Creek fell apart today

Date of Observation: 01/01/2023
Name: Zach Guy

Zone: Southeast Mountains
Route Description: Snowmobiled Cement Creek to the base of Hunter Hill.

Observed avalanche activity: Yes
Avalanches: Widespread and ongoing natural and remotely triggered persistent slab activity that appeared to start last night and go through today, localized to Upper Cement Creek (east of Deadman’s Trailhead). In that upper basin, almost every single steep slope that we rode near remotely avalanched if it hadn’t already gone naturally. Dozens of small creek beds released, and we triggered about half a dozen larger slopes just riding in the flats. More natural avalanches than I could count. Crowns were generally about 2 feet thick, and most appeared to fail on the mid-December facet layer. Small terrain features produced D1-1.5s, and larger terrain produced D2s. Avalanches were occurring on all aspects, which are generally E, SE, W, and NW below treeline in this basin. Couldn’t see the alpine.
Weather: Light snowfall with a few moderate pulses. Calm winds below treeline.
Snowpack: This might have been one of the most widespread, touchy persistent slab days I’ve ever experienced in my career; truly fascinating and blatantly dangerous. Human triggering felt almost certain. Riding into open slopes consistently produced rumbling collapses with trees shaking hundreds of yards away, shooting cracks opening on moderate angled slopes, and almost everything steeper than 35 degrees would slide. Collapses occurred on mid-December facets and depth hoar, which are now in the bottom 3rd of the snowpack below a 60 to 90 cm slab. Tests produced sudden collapses on isolation in the depth hoar (ECTPV). Near the trailhead, I watched a small dog step off the road and trigger a shooting crack across a slope. In Lower Cement, slabs are thinner (~30 cm), and better anchored by ground roughness, sagebrush, etc, thus the danger was less threatening.