Avy Hazard and Decision Making (from Cement Basin post)

Your right jtack, not every post needs/deserves analysis, commentary, critique.  But this one has evolved, maybe for everyone's benefit?

Respectfully Cookie and Amar, I differ with a couple of your conclusions.  
1) Surface observations, and photo's supporting, don't  tell a full story.  Seeing "well consolidation" from turns might just as well suggest a soft slab forming through settlement as well as stability, lacking other signs or tests.  And a slab over either a smooth or rough weak crust is not a particularly good indicator of stability.
2) Pete's CT test, a 7 with "fast failing on the rotten snow immediately under crust that the new snow had fallen on" tells me more.  Regardless, or perhaps because of, the bond between the new snow and crust surface, I am weighing in in support of Pete's conservative analysis and take on instability and thus their skiing more moderate slopes given all of their observations.
3) Is Bullion Peak, with its north face exposure, really that similar to East Peaks east and north  east exposures at EPk's slightly higher altitude?  Had the "moderate" winds gusting to 65 mph, out of the southwest to west,  over on top of Crystal the day before, effected Bullion Basin the same as the east slopes of East Peak.  Granted, as Cookie pointed out, none of the pictures showed evidence of  wind affect, although from the snow flying from skis, it wasn't light powder, but somewhat heavier.  Could you know that ahead  however,  before pushing off onto those east slopes?  Maybe, maybe not.
4) Does telemetry alone ever give us 'good to go'? With new snow and 'moderate' winds, gusting to 65, over some hours, why wouldn't one expect instability and look for it.  Only if all your observations indicated otherwise, right?
3)  "A slope which just got skied by several other skiers with no avalanche activity a real-world stability test  which is far better than any artificial stability test such as a pit."  Both are tests.  Both subject to spatial variability.  Both subject to the variability's that go with location, aspect, contour, tester, etc.  It all depends on what you're looking for the 'tests' to do - give you the go ahead to ski the slope, or give you pause to consider.  The problem with using skiing as a test, is that if your test indicates instability, well, you're in an avalanche.  Most experts look for test evidence to verify possibility instability, rather than stability.  Pete chose to back off rather than do more tests after he found suggestions of instability.  
4)  "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 slopes current stability under the load of a skier."  I can't differ strongly enough on this point.  Old tracks, new tracks, if there is an instability question, the newness of tracks means nothing.  It could mean you're more likely to find a weak spot triggering a slide, if for no other reason than we tend to want new tracks, not over or on top of the previous, so we are unintentionally testing more terrain for instabilities, increasing our probability of finding them if they exist.  If you remember, it wasn't that many years ago, in December on today's date, and not far away on the same greater slope,  that the 7th skier in a group of 7, as the last skier to start his descent, triggered a slab catching four skiers, partially burying 3 and totally burying 1 - who,  despite heroic efforts on the part of a partially buried partner to dig himself free, locate, probe and begin digging for that skier, was not recovered alive.   And this is the only reason we're having this discussion - to maybe help prevent it from happening again, anywhere.  We're really only skiing to have fun.

I would argue the telemetry/temperature impact on bonding is indeterminate, as the temp at 6800' when it started snowing was 24 degrees.  The slope above the hourglass chute in the lower photo, is around 5000' where there was a transition from rain to snow, but the large, steep face above it starts at ~6800.  Additionally, while the lower slope in the photo shows no signs of wind loading, the upper slope was definitely wind effected. Average ridgetop winds while snowing where between 10-20mph, the whole time...

12 25 1100 24 33 99 95 11 29 64 206 .03 .03 0 31

I would argue the telemetry/temperature impact on bonding is indeterminate, as the temp at 6800' when it started snowing was 24 degrees. The slope above the hourglass chute in the lower photo, is around 5000' where there was a transition from rain to snow, but the large, steep face above it starts at ~6800. Additionally, while the lower slope in the photo shows no signs of wind loading, the upper slope was definitely wind effected.  Average ridgetop winds while snowing where between 10-20mph, the whole time...

The slope above the hourglass chute in the dog photo is not near 5000 ft -- the chute is at roughly 6200 ft, and the flat clearing below is at 5900 ft -- the entire run is only 900 vert from the top of East Peak. See this topo map, with the crosshairs centered on the chute in question: mapper.acme.com/?ll=46.93954,-121.44712&z=15&t=T

There was no rainfall or rain-to-snow transition on any of these slopes. Even at the 4570 ft base of Crystal, the 33 °F temperature at the start of snowfall implies all snow and no rain. Especially considering that the RH prior to the onset of precip was only 39%, the strong evaporative cooling would have easily allowed snowfall to persist down to the ground even at temps in the mid-30s at onset.

Respectfully Cookie and Amar, I differ with a couple of your conclusions.
...
3) Is Bullion Peak, with its north face exposure, really that similar to East Peaks east and north east exposures at EPk's slightly higher altitude?

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3) The problem with using skiing as a test, is that if your test indicates instability, well, you're in an avalanche.  Most experts look for test evidence to verify possibility instability, rather than stability.
...

4) "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 slopes current stability under the load of a skier." I can't differ strongly enough on this point. Old tracks, new tracks, if there is an instability question, the newness of tracks means nothing.
...

I appreciate the discussion, Gerry. I have to say, this is really a lot of discussion for what was a very stable day, low-moderate avalanche hazard with no avalanche activity or incidents (or even near-incidents).

Re your first #3): Not sure why you think I'm saying that the N side of Bullion was similar to the ENE side of East Peak that day. I stated clearly that it was quite dissimilar. But that doesn't really matter too much.

Re your second #3): If others ski the slope as your stability testers, "you" can not be in an avalanche. Bruce Tremper refers to these as "volunteer stability testers" (p. 155 of Staying Alive in Avalanche Terrain, 2nd Ed.) and advises, "Never go first."

Re your second #4): I know that my statement is total anathema to the conventional avalanche wisdom, and figured that you would strongly disagree with it, Gerry (especially since you were one of the core group who initially taught me avalanche skills and ski mountaineering skills way back in 1997 -- something which I'll always appreciate). But my attitudes about avalanche skills and training have changed a lot over the years, for better or worse, and have often radically diverged from conventional avalanche wisdom where I suspected (or knew!) that it was wrong.

For example: everyone used to be taught to get rid of your pack if caught in an avalanche, but this is entirely wrong for a simple physics reason: all packs act like an airbag pack and help you float to the top of the debris deposit, because they are much less dense than the human body (generally 1/3 the density or less, e.g. a 30L day pack typically weighs about 10 kg loaded, even a 60L overnight pack is about 20 kg -- the human body weighs 1 kg per liter, same as water). Not to mention the protection from spinal injury provided by the pack. Thankfully, this bit of erroneous conventional wisdom is changing, and many newer books (like Tremper's) now advise you to leave the pack on -- although not for the correct physics reason of density reduction.

Another area in which I've strongly diverged from conventional avalanche wisdom is the constant emphasis on "beacon, probe, shovel" and the need to carry that on every trip. This is complete baloney -- the emphasis is all wrong, in both teaching and on real trips, it should be on avoiding avalanches either through choice of weather/snow conditions or choice of terrain/route, with rescue considerations secondary. There are many trips (even in winter and spring, not just summer) where the avy gear is totally unnecessary, but almost all bc skiers carry it anyway due to the powerful force of this conventional wisdom and its peer pressure. Yet most of them often omit other much more valuable emergency gear, such as a headlamp (or even better, 2 of them), extra batteries, a Jetboil stove, and a full down jacket -- "too much weight" or some such reason, but then why blindly carry avy gear?.

Recently skiing in a group of 14 (including several members of Mountain Rescue and guides) in mid-December in 1-2" new atop a solid crust (= near-zero avy hazard), we all brought avy gear due to blind convention, yet several of us neglected to bring headlamps or down jackets (and no one brought a stove) -- then we skied down the wrong drainage through navigational error in a whiteout, had to reascend over 2200 ft in the dark, and ended up having a near-epic, eventually getting back to the cars 7 hours after sunset. Avy gear is certainly not one of the ten essentials, even on winter ski trips -- so why is it treated as even more sacrosanct and never-to-be-left-behind?!? I will omit it if appropriate: in the past month alone, I've skied St Helens and 5 of my 6 trips to Camp Muir (4 solo) without bringing avy gear or having any need for it. Obviously on this day at Crystal with 9" new snow, we brought avy gear, but I would have lobbied strongly against avy gear if the new snowfall had been about 3" or less this day (given the prior 3-week drought and stable crust everywhere). Most everyone else would want to bring the avy gear anyway on such a day based on blind convention.

So back to the main point here: yes, it is conventional avalanche wisdom that following previous ski tracks is an unsafe and very bad practice. And it is all for the best that this particular point continues to be taught that way, since most of those following others tracks do so blindly and with little thought (and in sidecountry situations they often have little avy or snowpack knowledge).

But this conventional wisdom has a serious logical flaw: previous ski tracks which have set off an avalanche on a slope are considered among the strongest evidence of instability, as they should be. By the same token, previous ski tracks (prior skier loading of a slope in identical conditions, not so long ago that avy conditions have changed) which produced no avalanche activity are definitely strong evidence of a lack of instability. I don't see any way around this simple truth, as uncomfortable as it may be. The prior tracks may not be a guarantee of slope stability in generally unstable conditions (nothing is), but they are a most useful visual clue and should not be so blindly discounted.

Maybe in diverging so strongly from conventional avalanche wisdom, I'm becoming a dangerous ski partner who should be avoided -- so be it.

I like every part of this post. Too much armchair in this thread. Amar and Pete were there and both gave more than enough justification for their decisions.
While avalanche awareness and education are great, there is so much dogma that flies in the face of common sense.

The slope above the hourglass chute in the dog photo is not near 5000 ft -- the chute is at roughly 6200 ft, and the flat clearing below is at 5900 ft -- the entire run is only 900 vert from the top of East Peak. See this topo map, with the crosshairs centered on the chute in question: mapper.acme.com/?ll=46.93954,-121.44712&z=15&t=T

There was no rainfall or rain-to-snow transition on any of these slopes. Even at the 4570 ft base of Crystal, the 33 °F temperature at the start of snowfall implies all snow and no rain. Especially considering that the RH prior to the onset of precip was only 39%, the strong evaporative cooling would have easily allowed snowfall to persist down to the ground even at temps in the mid-30s at onset.


I appreciate the discussion, Gerry. I have to say, this is really a lot of discussion for what was a very stable day, low-moderate avalanche hazard with no avalanche activity or incidents (or even near-incidents).

Re your first #3): Not sure why you think I'm saying that the N side of Bullion was similar to the ENE side of East Peak that day. I stated clearly that it was quite dissimilar. But that doesn't really matter too much.

Re your second #3): If others ski the slope as your stability testers, "you" can not be in an avalanche. Bruce Tremper refers to these as "volunteer stability testers" (p. 155 of Staying Alive in Avalanche Terrain, 2nd Ed.) and advises, "Never go first."

Re your second #4): I know that my statement is total anathema to the conventional avalanche wisdom, and figured that you would strongly disagree with it, Gerry (especially since you were one of the core group who initially taught me avalanche skills and ski mountaineering skills way back in 1997 -- something which I'll always appreciate). But my attitudes about avalanche skills and training have changed a lot over the years, for better or worse, and have often radically diverged from conventional avalanche wisdom where I suspected (or knew!) that it was wrong.

For example: everyone used to be taught to get rid of your pack if caught in an avalanche, but this is entirely wrong for a simple physics reason: all packs act like an airbag pack and help you float to the top of the debris deposit, because they are much less dense than the human body (generally 1/3 the density or less, e.g. a 30L day pack typically weighs about 10 kg loaded, even a 60L overnight pack is about 20 kg -- the human body weighs 1 kg per liter, same as water). Not to mention the protection from spinal injury provided by the pack. Thankfully, this bit of erroneous conventional wisdom is changing, and many newer books (like Tremper's) now advise you to leave the pack on -- although not for the correct physics reason of density reduction.

Another area in which I've strongly diverged from conventional avalanche wisdom is the constant emphasis on "beacon, probe, shovel" and the need to carry that on every trip. This is complete baloney -- the emphasis is all wrong, in both teaching and on real trips, it should be on avoiding avalanches either through choice of weather/snow conditions or choice of terrain/route, with rescue considerations secondary. There are many trips (even in winter and spring, not just summer) where the avy gear is totally unnecessary, but almost all bc skiers carry it anyway due to the powerful force of this conventional wisdom and its peer pressure. Yet most of them often omit other much more valuable emergency gear, such as a headlamp (or even better, 2 of them), extra batteries, a Jetboil stove, and a full down jacket -- "too much weight" or some such reason, but then why blindly carry avy gear?.

Recently skiing in a group of 14 (including several members of Mountain Rescue and guides) in mid-December in 1-2" new atop a solid crust (= near-zero avy hazard), we all brought avy gear due to blind convention, yet several of us neglected to bring headlamps or down jackets (and no one brought a stove) -- then we skied down the wrong drainage through navigational error in a whiteout, had to reascend over 2200 ft in the dark, and ended up having a near-epic, eventually getting back to the cars 7 hours after sunset. Avy gear is certainly not one of the ten essentials, even on winter ski trips -- so why is it treated as even more sacrosanct and never-to-be-left-behind?!? I will omit it if appropriate: in the past month alone, I've skied St Helens and 5 of my 6 trips to Camp Muir (4 solo) without bringing avy gear or having any need for it. Obviously on this day at Crystal with 9" new snow, we brought avy gear, but I would have lobbied strongly against avy gear if the new snowfall had been about 3" or less this day (given the prior 3-week drought and stable crust everywhere). Most everyone else would want to bring the avy gear anyway on such a day based on blind convention.

So back to the main point here: yes, it is conventional avalanche wisdom that following previous ski tracks is an unsafe and very bad practice. And it is all for the best that this particular point continues to be taught that way, since most of those following others tracks do so blindly and with little thought (and in sidecountry situations they often have little avy or snowpack knowledge).

But this conventional wisdom has a serious logical flaw: previous ski tracks which have set off an avalanche on a slope are considered among the strongest evidence of instability, as they should be. By the same token, previous ski tracks (prior skier loading of a slope in identical conditions, not so long ago that avy conditions have changed) are definitely strong evidence of a lack of instability. I don't see any way around this simple truth, as uncomfortable as it may be. The prior tracks may not be a guarantee of slope stability in generally unstable conditions (nothing is), but they are a most useful visual clue and should not be so blindly discounted.

Maybe in diverging so strongly from conventional avalanche wisdom, I'm becoming a dangerous ski partner who should be avoided -- so be it.

So if it was below freezing when it started snowing, and there was wind blowing snow onto the slope and consolidating it, what evidence was there that the bond to the crust was good?  I'd like to understand why you guys think the avy danger was moderate/low when I can't figure out how its possible to tell how well the bonding was here....  I understand why a few tracks down the slope was re-assuring, but other than that, was there anything else?

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.

Re your second #3): If others ski the slope as your stability testers, "you" can not be in an avalanche. Bruce Tremper refers to these as "volunteer stability testers" (p. 155 of Staying Alive in Avalanche Terrain, 2nd Ed.) and advises, "Never go first."

Ah yes, this fellow is known as "Joe Gnarly Powder-Pig".  Oink! :