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Observation: Little Cottonwood Canyon

Observation Date
4/8/2018
Observer Name
Lees, Gagne, Wyatt
Region
Salt Lake » Little Cottonwood Canyon
Location Name or Route
Alta - Rocky Point - Sunset Dry fork
Weather
Sky
Obscured
Precipitation
Moderate Snowfall
Wind Direction
West
Wind Speed
Moderate
Weather Comments
Steady snow and winds all day, rain/snow line around 6,000' coming down the canyon.
Snow Characteristics
New Snow Depth
4"
New Snow Density
High
Snow Surface Conditions
Powder
Rain-Rime Crust
Snow Characteristics Comments

Snow was almost all graupel, and seemed elevation dependent - perhaps closer to 6 to 8" new above about 10,400'.

Travel conditions: yesterday's rain soaked snow refroze much faster than I expected. A lot to learn about these rain-on-snow events. The surface ice crust beneath today's new snow varied with elevation. Below about 10,000' it was a very hard, slick ice crust. Even though all of us had ski crampons, steep slopes, especially side hilling was difficult below about 10,000'. Super slick.

As you went higher, while still a hard and frozen crust, it was more like rough frozen snow than the slick icy rain crust.

Turning and riding was fun on super low angle slopes, in wind sheltered areas. Turning was best above about 10,000' where you could start to get on steeper slopes with out hitting the crust so much. Worse below about 10,000', where the crust was more like water ice.

Photo below: patches where the wind was scoring and drifting the snow. 9500'

Red Flags
Red Flags
Recent Avalanches
Red Flags Comments
Sluffs on slick crusts below about 10,000'. Common theme from a few observations from today is that the sluffs are initiating and running on lowerangled (< 30 degrees) slopes.
Avalanche Problem #1
Problem
New Snow
Trend
Same
Problem #1 Comments

Loose sluffs seemed the number one issue today, enhanced by a very slick ice crust beneath. Poor bonding of the graupel to the crusts below. Loose dry sluffs should be easy to trigger again tomorrow, especially below about 10,000'. Despite the wind, the snow didn't seem to be slabbing.

With the forecast of direct sun tomorrow, long running sluffs could even turn to long running wet loose sluffs, with denser debris piles.

Avalanche Problem #2
Problem
Wet Snow
Trend
Decreasing Danger
Problem #2 Comments

The snowpack is cooling much faster than I would have expected. I think wet slabs are unlikely until the next heating. We did find wet snow pooled in some places about a foot down, but it was very variable.

Photo below: an easily triggered sluff that ran quite far out on to low angle slope. While it picked up snow all the way down, it didn't propagate width wise. 9,600', west facing.

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