Observation: Mineral Fork

Observation Date
12/29/2015
Observer Name
Greg Gagne
Region
Salt Lake » Big Cottonwood Canyon » Mineral Fork
Location Name or Route
Mineral Fork
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
Northwest
Wind Speed
Calm
Weather Comments
Occasional S-1 snow showers. Virtually windless.
Snow Characteristics
New Snow Depth
1"
New Snow Density
Low
Snow Surface Conditions
Powder
Wind Crust
Snow Characteristics Comments

About 3-5 cms new (1-2"). Ski pens 10 cms (4") on a supportable base.

Depth of snowpack has settled to about 90 cms, with 100 - 100 cms above 9000'.

Likely the old snow surface was beginning to facet as we were able to easily get sluffs to move on steep slopes.

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

Will put "decreasing danger", but it seems to be decreasing a little more slowly than I'd like to see.

Comments

Touring today in mid elevations in Mineral Fork. Few in-your-face signs of instability. No collapsing or cracking, no recent avalanching since last cycle, no wind loading. General feeling is snowpack is showing signs of strengthening. However, on one pit on a north-facing aspect at 9000' on a 30 degree slope, we got an ECTP21/Q1. We repeated the test and scored ECTP24/Q1. In both instances the failure was in faceted snow down 1 meter at the ground.

This is classic deep slab instability. In other pits the last several days I have been unable to get an ECT to propagate, but on this slope the column did propagate. To me this is an indication that if you hit the right spot on a slope, it is possible to collapse the weak layer down near the ground and have the fracture propagate across the slope. But you have to hit the right spot.

Also worth noting interpreting these results is what I refer to as having "glass is half empty" view of the snowpack. If this is the only pit that shows instability, I pay far more attention to this pit than 20 others.

Video

In this photo one of my touring partners today (Tom Flaherty) is examining the faceted snow down at the ground. Overall we are seeing signs of this layer gaining strength, with some rounding of the facets. The grains were also somewhat damp and you were able to begin to make them into a snowball. But this process takes time.

I think today's forecast of a Moderate hazard is the right call. I think most slopes are stable, but from our pit results today, if you hit the sweet spot, large avalanches remain possible.

Fortunate to travel with such a strong team today (Erme Catino, Tom Flaherty, and Chino Rodriguez). No human factor issues going on - full propagation on ECT told us deep slab instability issues remain and we planned the remainder of our route accordingly.

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