Slate River

Date of Observation: 12/16/2021
Name: Evan Ross & Alex Banas

Zone: Northwest Mountains
Route Description: Slate River. NE, 9,000ft to 11,400ft

Observed avalanche activity: Yes
Avalanches: Nothing fresh since last weeks avalanche cycle. Of particular note, during the 12/10 avalanche cycle an avalanche had propagated from Run Away Ski, through the Lap Track Track Trees, and through most of Yogies. In my 14 or so years in this area I’ve only seen an avalanche go wall to wall across the lap track trees a few times. Cool or not cool?
Weather: Clear sky, becoming partly cloudy. Moderate wind gusts at ridge line transporting snow.
Snowpack: The Slate River Valley had plenty of wind-affected snow, but as soon as we started climbing into the avalanche paths out of the valley the snow surface was all lovely and unaffected by the wind event. Snow surfaces were soft even at ridgeline elevations. Ski pen around 25 to 30cm.

The snowpack in this area was greatly affected by the avalanche activity between 12/9 and 12/10. There wasn’t a lot of undisturbed snow out there. In those undisturbed areas, the persistent slab avalanche problem felt stubborn. We were able to get a few collapses, often with some extra effort.

On the slopes that had avalanche a week ago, I was eager to see if they were developing a new avalanche problem. Below treeline, I didn’t find anything concerning. Near treeline, there were some areas that did pose a concern due to the additional wind-loading.

Below treeline, I didn’t find anywhere that enough snow has accumulated on those old bed surfaces to create a new slab on the remaining facets. The average new snow depths on top of those old bed surfaces ranged from 30cm to 90cm. From a distance, it’s difficult to identify the slopes that avalanched on 12/9, while the slope that avalanche on 12/10 remained obvious.

Near treeline, the slopes that avalanched on 12/10, or generally later in the storm, didn’t pose much concern for a new avalanche problem on this tour. The slopes that avalanched early in the storm, around 12/9, were harder to identity that they had previously avalanched. Those slopes had seen enough wind-loading over the last week to start creating new slabs right near ridgeline. In the end, we didn’t avoid wind-loaded terrain, be we did make assessments and encountered heightened avalanche concerns in those areas.