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Observation: Grizzly Gulch

Observation Date
11/26/2014
Observer Name
Greg Gagne
Region
Salt Lake » Little Cottonwood Canyon » Grizzly Gulch
Location Name or Route
Grizzly Gulch
Weather
Sky
Clear
Wind Direction
Northwest
Wind Speed
Light
Weather Comments
Winds were light to occasionally moderate out of the NW, although I did not notice any snow being transported.
Snow Characteristics
Snow Surface Conditions
Dense Loose
Wind Crust
Rain-Rime Crust
Damp
Snow Characteristics Comments

HS in upper LCC is about 90 cms (36") and supportable. Winds from past two days took a toll on the snow surface where soft snow is hard to come by. Did find some thin rime crusts on a few NW aspects. South aspects were becoming damp when I was exiting the canyon in the early afternoon, and some rollerballs were noted. Fortunately low sun angle is preserving many slopes from the sun.

Red Flags
Red Flags
Recent Avalanches
Wind Loading
Poor Snowpack Structure
Red Flags Comments
Slide this morning on Patsy Marley was a hard slab due to recent wind loading, failing on faceted snow down near the ground.
Avalanche Problem #1
Problem
New Snow
Trend
Same
Problem #1 Comments

I was hopeful the weekend storm would help put the faceted snow and depth hoar in the bottom 20-30 cms (8-12") to sleep, but apparently not. I was still getting full propagation failures in extended column tests, with the best scores coming in at ECTP17, and ECTP6 on the low end; all were Q1 shears. (Video below.)

Avalanche Problem #2
Problem
Persistent Weak Layer
Trend
Same
Problem #2 Comments

It seems the strong winds from the past few days have overloaded some upper elevation shady slopes producing avalanches failing in the weak faceted snow down at the ground. Slide on Patsy Marley is a prime example.

Snow Profile
Aspect
Northeast
Elevation
9,400'
Slope Angle
26°
Comments

Photo is of unopened terrain at Alta showing obvious signs of wind loading. Video is extended column test showing full propagation with failure down near the ground.

Video

I went in to Grizzly to deploy some thermocrons to measure temperature gradients in the snow surface for our unwelcome period of high pressure. Decided to wander up to Twin Lakes pass to look at slides from this past weekend and noticed the slide that occurred earlier in the morning. (It had been reported, so I did not submit a separate observation.) According to Brett Kobernik, it was remotely triggered. It was an obviously wind loaded slope that was just waiting for a trigger. It failed in the weak faceted snow near the ground, and was a a pencil-hard slab with nasty chunks of debris.

Video

Photo is showing the debris with the remnants of ski or skin tracks. Video is at crown showing the obvious weak layer down near the ground.

Video

Overall poor stability tests and recent avalanches did not make me feel much better about our current snowpack. It seems our current weakness in the bottom 20-30 cms of the snowpack are going to be with us for awhile.

The glass-is-half-full view is that we actually have decent coverage and reasonable snow depths should begin to help heal our basal weaknesses from getting worse. We will have to watch what happens at the snow surface over the next few days as near-surface faceting is likely.

The glass-is-totally-full view is that our Wasatch looks absolutely beautiful right now. Happy Thanksgiving!

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