Avalanche: Turnagain

Location: Lipps

Route & General Observations

Lipps up to 3474′ for a couple of laps above treeline.

Avalanche Details
If this is an avalanche observation, click yes below and fill in the form as best as you can. If people were involved, please provide details.
Trigger SkierRemote Trigger Unknown
Avalanche Type Soft SlabAspect South Southwest
Elevation 3200ftSlope Angleunknown
Crown DepthunknownWidth 40ft
Vertical Run 400ft  
Avalanche Details

We witnessed a skier/rider trigger an avalanche on the south face of Cornbiscuit, a few minutes before noon. We were at least a mile away so details of this are just best estimates.

It looked to be triggered the 3rd rider down the face, of a party of 4. It seemed the rider was able to stop quickly and not get carried. The avalanche propagated about 40ft wide but 100ft down slope as well, and the debris running a couple hundred feet. It was close to the ridgetop but not immediately below it. The crown looked shallow and the debris soft, so perhaps it was confined to the new snow.
Attached are pictures but the quality is low so the avalanche is hard to make out.

Otherwise, a fair number of people ventured into steeper terrain today with only minor sluffing.

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?No
Observer Comments

The only red flag observed was the human triggered soft slab on Cornbiscuit.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.

*1F at the car at 11am but warming up upon return to 17* near 4:30pm.
A dynamic yet persistent layer of patchy valley fog was hanging out all day near the southern end of Turnagain Pass, shrouding us and then letting us free throughout the day. It mostly hung around from 2400ft - 2600ft. Blue skies above.
Light breeze coming from the SSW, or periods of calm. We observed flagging off Pete's North, but this was only occurring for a few minutes.

Snow surface

2-4mm surface hoar (observed from 1500', up to ridgetop) on top of ~2in of light new snow. Below this was a very thin and fragile crust, with more soft snow below.


We were wary of stepping out into big and steep terrain after seeing the recent avalanche on Cornbiscuit. The buried surface hoar was also present on our minds. We dug a quick test pit at 2400' to aid our decision making. It was on a 20* SW facing slope, adjacent to the slope we intended to travel on.
We dug 1 meter down, and the buried surface hoar was easily identifiable in our pit walls, 65cm below the surface. With closer inspection, it appeared the grains were laid flat and rounding.
In our tests, we only got the surface hoar to fail with a column test, outside of test parameters (using extra force), but once it did fail, it sheared in a sudden planar fashion. Otherwise, we got benign results with our stability tests (various ECTN and CT_PC within the top 15cm of soft snow).

Photos & Video
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