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Observation: Shingle Mill

Observation Date
12/31/2021
Observer Name
Mark Staples
Region
Uintas » Shingle Mill
Location Name or Route
Mud Flats area
Weather
Weather Comments
Cold and snowy. About 3-4 inches accumulating during the day. There was a period of an hour or two when the sun tried to come out in the middle of the day. Winds at 9800 feet were light.
Snow Characteristics
New Snow Depth
12"
New Snow Density
Low
Snow Surface Conditions
Powder
Red Flags
Red Flags
Heavy Snowfall
Collapsing
Poor Snowpack Structure
Red Flags Comments
Snowfall in the last week contains 7.2 inches of water. This amount of water over an area the size of a football field equates to 2,500,000 pounds. Imagine that amount of stress on the weak layer at the ground. If that weak layer breaks, imagine 2,500,000 pounds of snow crashing down the mountainside.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
This is the #1 problem. It's scary now and perhaps for the coming week or so. The good news is that it doesn't exist on south facing slopes. The other good news is that the skiing and riding is 5 star on all aspects and all elevations which means we have terrain options to choose from.
Snow Profile
Aspect
Northeast
Elevation
9,500'
Slope Angle
29°
Comments
I was surprised how easily the ECT broke and propagated. It was on my last tap swinging my arm from the elbow (ECTP20), but I thought that I was going to have to give it hard taps swinging my arm from my shoulder becuase the weak layer has such a thick slab on top of it.
However, this thick, supportable slab made it a little harder to have widespread collapsing. We heard several collapses, including a very loud, tree shaking collapse.
Let me make a key point - triggering a collapse IS EXACTLY THE SAME AS TRIGGERING AN AVALANCHE. The only difference is that the slope is not steep enough to slide, so you don't get an avalanche. However, all the other processes in an avalanche occur in a collapse.
Video below shows how deep the new snow is. Unbelievable.
Video
Comment about the danger rating -
There are several ways to think about avalanche danger. View the danger scale below. Notice the columns labled "travel advice", "likelihood of avalanches", and "avalanche size and distribution".
The travel advice for HIGH danger fits our current situation on northerly facing slopes (as well as W, E, and SE) very well - "Very dangerous avalanche conditions. Travel in avalanche terrain NOT recommended."
Today's Observed Danger Rating
High
Tomorrows Estimated Danger Rating
High
Coordinates