Professional Observation

Basic Information

Observation Date:

December 10, 2021

Submitted:

December 10, 2021

Observer:

Chris Engelhardt | ESAC Forecaster

Zone or Region:

Mammoth Lakes

Location:

Sherwins- above Mammoth Rock

Recent Avalanches?

Yes

Cracking?

Isolated

Collapsing?

Isolated

With touring options very limited at this point, headed back up to the Sherwins above Mammoth rock. There is not much more than 6inches of snow in a majority of the terrain until you hit about 9300ft on northerly aspects where depths start to increase. I tried to skin up through some larger glades and steeper terrain than I did yesterday on the Minaret Vista. Many of these larger panels of snow audibly whoomphed and collapsed when I skinned across them with some associated surface cracking.

There was also evidence of several mid-storm soft slab avalanches that had slid right from ridgeline or just below ridgeline on N-NE aspects. The Mammoth Rock Bowl and Main Avy Path were the terrain features where I observed these. Crowns looked to be around a foot in depth and were 40-50feet across. These small D1 slides ran 100-150feet vertical and put some minor piles of debris up against the trees.

I saw a few small point releases as well off the Mammoth Crest near TJ Bowl and Hammil bowl that had run a few hundred vertical feet.

Stability Rating:

Fair

Confidence in Rating:

High

Stability Trend:

Steady

Advanced Information

Cloud Cover:

Clear

Temperature:

-6.5

Wind:

Calm

Overall snowpack depths ranged from 50-80cm within the elevation span of 9300ft elevation up to ridgeline ~ 10000ft. Below 9300ft there is only 15cm of snow, just barely enough to offer some purchase to skin on today. New snow from the little storm on 12/7 and the bigger storm 12/9 totaled 25-35cm on average above 9300ft elevation. Bottom line is that the old snow in this sheltered, tree’d terrain is very faceted and weak. When I got off my skis to dig a snow pit I went all the way through the snowpack to the ground. Yesterday’s storm was still very soft (Fist hardness) in this area and had not slabbed up yet under our current cold and calm conditions. I did get two consecutive ECTP21 results at the new snow/old snow interface. The old snow surface has a capping melt freeze layer and the propagating results failed underneath this crust in the faceted snow below ~35cm below the surface. If we do get a significant storm with a lot of weight next week there is no doubt that this old rotten snow will fail. Hopefully the impending storm is significant enough that a lot of this old degraded garbage snow will get flushed out mid-storm, we’ll see what happens.

https://www.youtube.com/watch?v=mtKymRJssuI