Observation Date
12/21/2014
Observer Name
Bruce Tremper
Region
Salt Lake » Big Cottonwood Canyon » 10420
Location Name or Route
Peak 10,420
Weather
Sky
Overcast
Precipitation
Heavy Snowfall
Wind Direction
West
Wind Speed
Strong
Weather Comments
Wow, I absolutely LOVE being out in big storms. Just get out there and TAKE IT. Nuking wind, heavy snow, upside down snow, wind slas, rapid loading. It's the kind of weather avalanche forecasters are born for. The rain-snow line rose throughtout the day up to around 7,500' --maybe briefly up to 8,000'--by about 3 pm when I came down the canyon.
Snow Characteristics
New Snow Depth
10"
New Snow Density
High
Snow Surface Conditions
Powder
Snow Characteristics Comments

Freezing levels rose through the day along with the very strong wind, causing the new snow become progressively more upside down and slabby. Wind from the west stripped all the snow off the windward side and quickly created dense wind slabs in downwind terrain. Even in the thick trees, there were whale backs and lurch and jerk skiing conditions. Tricky. But we really need some dense snow this time of year for good coverage.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Collapsing
Rapid Warming
Poor Snowpack Structure
Red Flags Comments
Yup, pretty much got em all. I guess it must be dangerous out there, if you believe those stupid avalanche books anyway.
Avalanche Problem #1
Problem
New Snow
Problem #1 Comments

In conditions like these it's hard to know which avalanche problem to pick because they're all mixed up together. But according to our flowchart on the wall, we're supposed to call any slab on top of a persistent weak layer a "persistent slab" whether it's a wind slab or storm snow. So we have storm snow and wind slabs on top of a persistent weak layer--whatever you want to call it.

It's hard to tell whether the slabs are breaking on top of the pre-existing faceted layer (with surface hoar mixed in) or on the low density snow just on top of the faceted layer. Not that it makes any difference except to avalanche geeks, but then again, I don't even care. Stiff, dense, warm slabs are overloading weak snow underneath them. That's all anyone needs to know. I notice that the snow started yesterday without hardly a breath of wind on the high peaks, so much of the low density new snow is probably preserved. Just under that is weak faceted snow, continues all to way to the ground in areas with less than about 50 cm and has a supportable layer in places deeper than about 50 cm.

Comments
Today's Observed Danger Rating
High
Tomorrows Estimated Danger Rating
High