Avalanche: Turnagain

Location: Pete's North

Date:

March 23, 2022 10:07pm

Observer:

Sykes / Dahl Forecaster

Route & General Observations

We went up Pete’s North to 2000′ to check out storm totals and hunt for buried surface hoar, which we found to be quite reactive.

Avalanche Details

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Trigger	Skier	Remote Trigger	No
Avalanche Type	Soft Slab	Aspect	West
Elevation	2000ft	Slope Angle	37deg
Crown Depth	14in	Width	80ft
Vertical Run	50ft

Avalanche Details

We triggered two soft slab avalanches that failed on the 3/16th buried surface hoar with crown depths from 30-40cm. One failed just as we were about to start digging a pit, and another while we were descending. They both broke at our feet. We estimated the first one to be 75-100' wide and the second to be around 60'. For both avalanches, we were able walk/ski above the crown and easily get additional, substantially sized chunks to slide.
They were both on a west aspect at 2000'. We measured the slope angle at the trigger point of the first to be between 37* & 38*. They both were on relatively small terrain features so they only ran a short distance before stopping on lower angle terrain.

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)?	Yes

Observer Comments

We triggered two avalanches. The only red flag we observed was subtle cracking a few steps before triggering the first avalanche. The snowpack at the site of the avalanches seemed quite touchy; we were able to walk/ski above the crowns and get significant portions of the slope to slide.

Weather & Snow Characteristics

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

Weather

Stormy weather. Skies ranged were mostly obscured or overcast. There was a short window of thin cloud cover with decent visibility.
Temps at the trailhead were 33*F, with moist snow on the surface up to 1200'. Wind gusts from the north were strong enough to blow snow around at the surface and knock snow off the trees.
Snowing on and off through out the day, up to S1.

Snow surface

4 inches of new moist snow up to 1200', then about 6-8inches of dry-ish new snow above 1200'.

Snowpack

The 3/16 layer of buried surface hoar proved to be reactive to human triggers with our avalanches. It seems to be a touchy layer of concern.
We dug a pit at the site of our first avalanche (West aspect, 2000').
We found 3 layers of buried surface hoar from this month within the upper snowpack. All three layers failed in our compression tests but only the 3/16 BSH had propagating results when we performed an ECT. Depth of the layers of surface hoar and their test results below:
3/22 BSH: 20cm below the surface, 1-2mm. CT9, ECTN7.
3/16 BSH: 35cm below the surface, 3-6mm. CT11 SP, ECTP13, & ECTP15. This is the layer our avalanches failed on and seems to be the most problematic, especially with more snow forecasted.
3/2 BSH: 48cm down, 1-3mm, rounding. CT13, ECTN20.

Photos & Video

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