Observation Date
12/30/2017
Observer Name
Derek DeBruin
Region
Salt Lake » Little Cottonwood Canyon » Grizzly Gulch
Location Name or Route
South of Michigan City, above the summer road
Weather
Sky
Overcast
Wind Direction
Southeast
Wind Speed
Moderate
Weather Comments
Wind shifted and air temperature dropped as we were working this afternoon; the front seems to have started passing.
Snow Characteristics
Snow Surface Conditions
Faceted Loose
Snow Characteristics Comments
Pretty good surface conditions for riding; near surface facets of 2 to 3mm in size on top of progressively harder snow beneath.
Red Flags
Red Flags
Poor Snowpack Structure
Red Flags Comments
The snowpack is still a recipe for disaster. We found snow depth up to 170cm with right side up snow in the top meter, resting on a deteriorating crust with a series of crusts and facets beneath. I imagine Locations with shallower snowpack might be more touchy, though not terribly so.
Bridging seems to be happening with the cohesive upper portion of the snowpack. Compression test failed at the ground quite readily on the 16th tap; however, ECT did not propagate. Investigated the uppermost crust 82cm from the bottom with a propagation saw test and got a full and clean propagation at 99/100. My hunch is that it would be possible to trigger something on the uppermost crust that could then step down, but the test results seem to indicate bridging. I'm hedging my bets and keeping to low angle terrain, not trusting the persistent weakness, and waiting to see what happens with additional loading (whenver that comes next).
Avalanche Problem #1
Problem
Persistent Weak Layer
Problem #1 Comments
See above. Tests indicate bridging in the upper snowpack, but the mess of crusts and facets beneath provide the opportunity for avalanches that could step down to the ground.
Snow Profile
Aspect
North
Elevation
9,600'
Slope Angle
33°
Comments
Near surface facets and right side up melt forms bridge over a thin crust 82cm above the ground. Below this is a series of crusts and facets; facets are rounding but some are rather large. Crusts are decomposing with clustered melt forms. There is a distinct, hard crust 25cm above the ground that crumbles readily when prodded.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable
Coordinates
