Avy Hazard and Decision Making (from Cement Basin post)

OK Amar I'll bite.  But first, nice report, good analysis, as we've come to respect and expect from you.  Excepting maybe your rationale for skiing off the East Peak?  "We were just planning to ski the SW side, but decided to ski the steeper NE and ENE aspects (30-40 degrees) from the summit of East Peak only after seeing a handful of ski tracks having already descended safely down this aspect (another obvious big avy slope)."   Seeing tracks leading down an avy slope isn't any kind of assurance or insurance that it won't slide when it's shred again, right?  Having dug no pits, could you be assured it wasn't  different than the north face of Bullion?  Granted, the evidence was accumulating that what you expected and found, was stable. But since I've started and you've responded re this analysis, dare I ask if it's good practice to be standing shooting a photo upward when both your dog and fellow skier is descending an avalanche slope from directly above you? 

The above said  Amar, I value your contribution to this post and dialogue, which perhaps I could have/should have conducted in that alternative category Marcus established to explore avalanche safety and understanding - but this extended thread has, in my opinion, turned out to be a valuable learning experience for anyone reading it - or posting to it!  More importantly, it was a great ski day for all of you participating.  Also Pete, in my last post I wasn't inferring that you were 'at the beginning of your backcountry experiences', but instead referred to those readers who's experiences in the backcountry are new and building.    Happy New Year All.

You can see the snow is stable in the photos, and the telemetry explains why. Some more obs:

* Some of Pete A's photos clearly show snow with minimal wind signatures on the surface.
* In the first photo by Pete A, notice the lack of a drift line near the pine tree.
* In the first photo by Pete A, notice the micro-scale terrain features are visible below the new snow: settlement.
* Notice the uniform collection of snow on the trees in Pete A's first and second photos.
* Notice the lack of drift lines in the other photos.
* Amar's photos also show a lack of drift lines.
* Look at the ski tracks, especially the inside of the turns. The snow is clearly well-consolidated.
* The telemetry data posted by Amar contains a very obvious clue as to why they all found low instability.
* Examine the telemetry: look at temps/RH/wind.
* Bonding between existing snow and new snow: surface roughness is key, including variations at small scales.

OK Amar I'll bite. But first, nice report, good analysis, as we've come to respect and expect from you. Excepting maybe your rationale for skiing off the East Peak? "We were just planning to ski the SW side, but decided to ski the steeper NE and ENE aspects (30-40 degrees) from the summit of East Peak only after seeing a handful of ski tracks having already descended safely down this aspect (another obvious big avy slope)." Seeing tracks leading down an avy slope isn't any kind of assurance or insurance that it won't slide when it's shred again, right? Having dug no pits, could you be assured it wasn't different than the north face of Bullion? Granted, the evidence was accumulating that what you expected and found, was stable.

Actually, some of the skiers who had made the tracks were only minutes ahead of us, we could see them on the flats far below. A slope which just got skied by several other skiers with no avalanche activity is very solid assurance of its stability: it is a "real-world" stability test which is far better than any artificial stability test such as a pit. Seeing old tracks down a slope may be no assurance of stability, but seeing fresh tracks only minutes old is the strongest possible evidence of a slope's current stability under the load of a skier.

The slope and snow conditions were in fact very different than the north face of Bullion, as should be expected given the different aspect and much less exposure to this storm's winds. Much deeper snow right from the top, but no windcrust, less steep at the top, etc. -- it seemed likely that this slope was more stable today than the N side of Bullion. If there had been no previous tracks, we probably would have skied it by taking one of the more conservative and less steep lines which start farther NW from the summit of East Peak, leading down a broad shoulder towards open timber, instead of the big open slope leading to an obvious gully.

But since I've started and you've responded re this analysis, dare I ask if it's good practice to be standing shooting a photo upward when both your dog and fellow skier is descending an avalanche slope from directly above you?

Photos can deceive the eye. The dog is actually over 20 ft away from me, the photo has been cropped somewhat. And I'm not standing directly on that avalanche slope at all, but on a small knob (a few feet high) at the skier's left edge of the open slope, an obvious "safe zone" to wait for subsequent skiers to descend. I am not in the fall line of any possible debris, which would run to my left (skier's right of me).


[hr]The telemetry does really explain the stability: temps starting near freezing and consistently falling throughout the period of snowfall, ensuring a good bond to the underlying crust and a very right-side-up density profile of the new snow.

In addition, the previous crust was not smooth (except on steep south aspects), ensuring a better bond: this was a long-term settlement crust due to 3 weeks of minimal precip, rough and bumpy -- there was no smooth icy rain crust at all, and a smoother sun crust only on steep south aspects, which did produce minor instability on the upper windswept parts of the SW face of East Peak (slabbing off of thin layers of windpacked new snow).

Good discussion Boys

While I have enjoyed the discussion, I do not expect a full avalanche report every post, I was happy to see the great pictures, and glad someone was having some good skiing. I think every skier is responsible for making their own safety decisions. If someone is nice enough include some beta, I'll be happy to conceder it.

Thanks for the pics Amar and the fun trip as usual! You captured the Brown family really well. Steph was making some really nice turns in the third pic!