Avy Hazard and Decision Making (from Cement Basin post)

Now that its again snowy, we can all go back to some great skiing.  Looking forward to the outrageous posts in the next few days.  

Of couple of quick last comments.  It seems your last several questions Eli3 were well answered by Amar.  Amar is spot on in describing the value of keeping the pack on in an avalanche.  The increased volume hypothesis is also called the 'mixed nut' event.  Shake the can of mixed nuts and the big ones always end up on top, regardless of their density/weight; so too in a running avalanche, which is considered a granular laminar flow, rather than a liquid (as we float when carried down the river).   So keeping the pack on makes us a bigger nut in the can, in the flow, hence much more likely to end up on top.  This is the exact theory of the airbag deployment, which both makes us rather instantly larger,  and provides protection - to a limit.  The people I've talked with and read of who've survived avalanches when carried into trees have usually spoken well of having their pack on to help reduce the impact - if they were lucky enough to hit back first. And most needed the supplies in their pack for first aid, survival and rescue, as well. There is a growing body of incident evidence showing likely improved survival rates in Europe of those caught in avalanches and deploying airbags.  They won't help you however if blasted through the trees, caught in a really big avalanche or carried over, into & through other terrain traps (over cliffs, into rockfall or crevasses; there were a number of Euro's, including an entire family, who died wearing airbags last season in France.

Amar, the points you make re avalanche gear and other potential helpful survival gear are spot on.  I think many of us wrestle with the same questions.  Myself, as a habit, I always wear my beacon, even during the spring-summer cycle.  I don't know, maybe I figure it will help someone find me if I plunge through a bergshrund, fall in a moat or creek, etc.  I usually go to a shorter probe (lighter), and may even drag out my old 'plastic' Life Link shovel (whose blade has never failed, but handle has bent), because it's sometimes nice to dig a perch or lunch table.  Your comments re other pack contents are well said.    

To me one of the most important takeaways (in addition to what Cookie Monster just posted and said so well, while I was writing this) from this series is the communications, analysis and considerations that went on within Pete and Amar's parties, in making the decisions they did.  Both made good decisions.  If I was with Amar and party, I probably would have argued for digging a quick pit on a good spot before taking the plunge down the eastside of East Peak, but, that might just be me.  I've certainly become a little more conservative, ski-wise, as I've gotten older.  So I look forward to when we can ski together again Amar, we've always had fun and come back intact.  Thanks for your patience with me in asking my questions, and for taking the time to respond and ask yours!  Its been a good dialogue.  I'll not start this again.......   Cheers and a Happy New Years skiing to all.  Gerry

We were up there that day and and agree it was very stable, unconsolidated fluff on hard pack with no slab formation, as stable as I've seen it in 30+ days in the area.   RJ

Well, if we're going to analyze the avy hazard and decision-making here, might as well link to the available forecasts and data for reference:

Danger rose for all zones near and west of the Cascade crest:
http://www.nwac.us/dangerrose/preview/2043/

I'm also not convinced how a wearing a pack would help flotation in an avalanche.  I see how it would protect the spine, but the density of the pack is probably going to be denser than the snow in motion - while this would slightly reduce the skiers average density, it makes them heavier and bulkier, making it harder to stay on top of the snow.  I guess i'd have to see statistics similar to the airbag ones to believe this.

You are wrong and Amar is right. It's physics and has nothing to do with being denser and heavier and sinking...it's all about being larger when wearing a pack. Research the physics of why avy air bags work to keep you on top and you will understand.

Amar is also right IMHO that previous ski tracks can be a sign of stability....good for you Amar for flying in the face of convention and dogma. Welcome to the dangerous skier club. ;D

Here are my thoughts they are mine alone. Some of us take less risk and are conservative. Some of us take more risk and are fine with it. I have been in both camps. As long as we don't injure each other life is good. As a member of this community I feel a responsibility not only to my skiing partners but to the rest of the community to carry my avy gear at all times. Most of my avy gear is not for my safety it is for the safety of others i.e. the community. I want to be able to help out if someone else happens to step on that sweet spot in a slope and gets an unexpected ride.

This guy probably thought the recent ski tracks right next to his line were a good sign of stability.

It's obvious that the skier triggered this slab from a shallow point in the snowpack (look at the video at 1:25) but it would have been difficult to know the buried rock rib was there prior to the avalanche.

In my opinion, recent tracks may be a good sign of stability when dealing with storm slab or loose snow but applying this logic to other types of instability could get you into trouble.

This guy probably thought the recent ski tracks right next to his line were a good sign of stability. 

It's obvious that the skier triggered this slab from a shallow point in the snowpack (look at the video at 1:25) but it would have been difficult to know the buried rock rib was there prior to the avalanche. 

In my opinion, recent tracks may be a good sign of stability when dealing with storm slab or loose snow but applying this logic to other types of instability could get you into trouble. 

Good thoughts, Jeff.

I wouldn't argue that this slope, the "Hourglass" wasn't reasonable on this day given first hand accounts of a relatively shallow amount of recent reported "unconsolidated snow" overlying a crust that likely limited the depth of any potential slide. I've skied it once myself in similar conditions, though later in spring.

I would say, though, that this slope is a great example of an extremely high consequences slope, one that if one were to make an error in judgement, is likely to be injurious or deadly. It is a gereat example of a slope that one wouldn't want to make a habit of skiing.