Observation: Mineral Fork

Observation Date
1/6/2016
Observer Name
Greg Gagne with Dave Pease
Region
Salt Lake » Big Cottonwood Canyon » Mineral Fork
Location Name or Route
Mineral Fork
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Speed
Calm
Weather Comments
Very warm & muggy conditions. Windless. Some on and off snow showers depositing a trace.
Snow Characteristics
New Snow Depth
2"
New Snow Density
Medium
Snow Surface Conditions
Powder
Dense Loose
Faceted Loose
Wind Crust
Damp
Snow Characteristics Comments

The 5 cms (2") that has fallen the past few days has done wonders for the ski conditions. On northerly elevations above about 9000' the new snow has fallen on an old snow surface that began faceting right after the New Year. The little bit of dense new snow was sluffing easily at this interface on slopes steeper than about 35 degrees. This is not a current avalanche problem, but it's worth watching if the old snow surface becomes a weak layer.

Below 9000' was not finding the old snow surface to be especially weak.

Below about 8000' the snow surface is damp on all aspects.

HS ranges from 60 cms (2') on South & West aspects at 8000' to 150 cms (5') on Northerly aspects at 10000'

Red Flags
Red Flags
Poor Snowpack Structure
Avalanche Problem #1
Problem
Persistent Weak Layer
Problem #1 Comments

I think the deep slab remains our current and only avalanche hazard right now.

Snow Profile
Aspect
Northeast
Elevation
9,800'
Slope Angle
35°
Video

Video shows ECTP25 that failed in facets down near the ground. This was on a 35 degree slope on a NE aspect at 9800'. HS was 150 cms in this location, with 30 cms of facets down near the ground.

(Location was Bengal Tiger in Mineral Fork on Wasatch Backcountry Map.)

A good question is: How do we interpret these results?

There is 130 cms of snow over the weak layer, so I suspect a skier could not trigger a slide in an area with a deep snowpack such as this. But getting propagation with energy is still a sign avalanches are possible on this weak layer, though not likely. You would likely need to trigger one in a thinner snowpack area, which could propagate.

Bottom line was that we have a Moderate hazard in upper elevation northerly terrain, and it's not green light/ski-it-if-its-white conditions. Large, deep slab avalanches remain possible.

Also found the layer of basal facets interesting. In most areas I've been looking at this layer has compressed to 5-20 cms (2-8"), but this layer was 30-35 cms (12-14"). It was 4F hard, so is showing signs of strengthening.

Much of the upper headwall of Bengal Tiger had slid during the Christmas cycle (likely sliding on 12/23.) The bed surface is similar to what I (and others) have been seeing. It feels very much like an early November snowpack: it is thin (15-30 cms) (6-12") and mostly faceted. Although skiing old bed surfaces was a wise choice following the Christmas storms, these paths are prime to be repeaters once they receive a new load of snow and/or wind.

I think most of the terrain is generally Low, with isolated pockets of Moderate on upper elevation West through East.

Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Moderate
Coordinates