Observation: Turnagain

03/27/13
Observers: Sean Fallon and Graham Predeger
Location: Seattle Ridge

Weather:
Sky-Clear with high clouds developing in pm
Wind- Calm
Temp- 5F in parking lot at 11:00am, 21F at 4:30pm
Precip-None

Signs of Instability:
Recent Avalanches- we saw small shallow wind slabs pull out all over the pass. One
on Sunburst gained some mass and stepped down to a lower crust. From the parking lot it
looked to be 100-200 feet wind. Most others were less than 50 feet wide, and slow
running.

Surface Conditions:
The surface snow is highly variable with some areas containing a breakable wind slab
on top of light powder. Other areas stayed sheltered and have light blower snow. It’s hard
to predict how soft the snow will be just by looking at it. Snow that looks wind affected can
be quite soft and snow that looks untouched can be a wind board.

Comments and Concerns:
Graham and I explored all over Seattle ridge today. We found many small easily
triggered wind slabs. Even though the winds from Monday’s storm were relatively light, the
cold, low-density snow slabbed up easily. The slabs are generally 6 inches thick and run
on last Saturday’s sun crust. Occasionally they step down 20 cm to an older crust. On one
of our runs, I ski cut above a NW facing gully and nothing moved. But three turns in, the
gully slid. The crown was about 40 feet wide, six inches deep and it traveled 300 feet on a
38-40 degree slope. It took all the snow off my run. On our way back to the truck, we
checked out a 50 foot wide skier-triggered slide on repeat offender, that likely occurred
yesterday and ran across the up-track. When we approached the slide, we triggered a
similarly sized slab next to the older crown, although it didn’t run as far. All the slides we
saw were small and manageable, but could be dangerous in exposed terrain.