Observation: Big Cottonwood Canyon

Observation Date
12/15/2018
Observer Name
Andrew McLean
Region
Salt Lake » Big Cottonwood Canyon
Location Name or Route
Upper Big Cottonwood Canyon
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Decreasing Danger
Problem #1 Comments
The bottom 20-30cm of rotten, faceted snow isn't going anywhere on high, north faces, but the good news is that the upper 90cm of snow has settled into a strong, cohesive slab and it will be increasingly difficult to get slides to pull out. I think the main areas of concern right now would be wind loaded slopes on upper, north facing slopes which are unsupported from below or the sides, like a big hanging snowfield.
Snow Profile
Aspect
Northwest
Elevation
9,500'
Comments
The warm days and cold nights have definitely strengthened the snowpack. We toured in upper BCC today from about 8,500' to 10,000' and saw no signs of cracking, collapsing, or natural avalanches. The surface snow was consolidated powder, which the wind had jacked around quite a bit. Sheltered north facing snow was good, but anything with sun or exposed ridgelines were getting punchy and/or crusty.
Pit #1
9,894' Northwest Facing, 32 degree slope
Total depth - 10cm
Aside from the 20cm of basal facets, the overall structure was good - 50cm of fist, then 4F all the way down to the facets.
ECT test of nil/30
Compression test of nil/30
The 90cm of snow is gaining a lot of strength, but still has a few cm of skiable fluff on top. We skied a short little due north couloir with a steep entrance (35-42 degrees) with a bit of windloading and there was no movement. The snowpack has lost about 15cm due to settlement in the last week or so.
The skiing was good, but swirly winds and sun has crusted up many of the slopes. The best skiing is in a narrow band of not too high (wind blown tops), not too low (not enough snow), sheltered, north facing slopes.
I think the danger is low on most slopes, but there could still be a few areas up high where it would be possible to trigger a slide, although you'd really have to be looking for them.
Today's Observed Danger Rating
Low
Tomorrows Estimated Danger Rating
Low