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Observation: Snowbird periphery

Observation Date
3/6/2016
Observer Name
Zimmerman-Wall/ Snowbird AIARE 1
Region
Salt Lake » Little Cottonwood Canyon » Snowbird periphery
Location Name or Route
Sinner's pass/ AF Canyon
Weather
Sky
Obscured
Precipitation
Light Snowfall
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Rain below 8000 feet on the way up LCC at 7am. Warm temps seemed to have kept the old snow surface from freezing solid up to about 10,000. Precip was falling as wet flakes up to about 9000 feet and gave way to graupel for most of the day. The winds were ripping out of the SW until about 13:00, when they began to shift more Westerly and then taper off for about an hour and a half. The sun even broke through the clouds for a short moment and it was eerily calm along the highest ridge lines for about twenty minutes. Then the black wall of the frontal passage came over the valley by 1600 and some very large graupel and strong westerly winds began blowing.
Snow Characteristics
New Snow Depth
4"
New Snow Density
High
Snow Surface Conditions
Powder
Damp
Snow Characteristics Comments
The new snow appeared to bond quite well to the old snow surfaces where the winds hadn't stripped it away. The old surfaces ranged from semi frozen corrugated mank, to smooth melt/freeze crusts depending on aspect and elevation. Down low it was apparent the new snow was insulating the saturated old snow and it was a sloppy, messy, goop that stuck to every thing it touched. Above 9500 feet, the graupel had really filled in a lot of old tracks/trenches, especially in sheltered terrain. This made the skiing supportable and fast and it remained quite good in the untracked areas all day long.
Red Flags
Red Flags
Wind Loading
Red Flags Comments
The wind loading was the main concern for our groups, as we purposely avoided low elevation steep terrain where the danger of triggering a disgusting wet loose lava flow was more pronounced.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #1 Comments
New cornices were forming atop old sagging cornices along ridges between 10-11k. No cracking was observed during our travels, but will be giving these a wide berth in the days to come. Some small pillows and drifts (30-50cm deep) were also forming off the ridgelines on leeward slopes and terrain features.
Avalanche Problem #2
Problem
New Snow
Trend
Increasing Danger
Problem #2 Comments
It was interesting to observe the storm slab (albeit only 10-15cm deep) forming before our eyes. Especially out of the wind zone where the snow was falling on smooth surfaces. We were getting resistant shears in our hand pits and even a couple CTM and CTH results. The shears were Q3 failing on some of the smaller graupel from the beginning of the storm, running on the smooth, decomposing temperature crusts. This was not a true problem and was easily managed by our group. However, it may become something to be cognizant of if the forecast produces and we get that 1"+ of H20. Be cautious of venturing into steep committing terrain where a small pocket would take you into trees or off a cliff.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Moderate