Anthracites Playground 2-11-24

[muted reborn]

Maybe chill a bit on the assumptions. It was a tragic accident. Mistakes were made. People are grieving.

Be humble. Learn. Thanks

If you want to call out someone specifically for an out of line comment, go for it, but don't guilt trip us all and shut down an informative thread where most people actually are being humble and learning.

[ballackout]

I disagree that my thoughts were inappropriate or aimed at anything other than learning (to the extent Foggy was responding to me). But I've deleted my comment.

Again, my condolences to all involved.

[Foggy_Goggles]

Incident debreifs often step into the hypothetical. Thats OK. Opining on what those involved where thinking is not. Its just my opinion.

I've been in this game a minute. The enemy is us. In retrospect, it is frequently easy to identify the mistakes. If you think you or your group would never make those mistakes, excellent. But you are probably wrong. Consistently conservative decision making from a position of hyper awareness is the game for the experience. Just because it's obvious don't mean it is simple. If you extrapolate it over your entire backcountry skiing career, it becomes incredibly difficult.

I'm not guilt tripping anyone. If you don't think it applies you your comment, that's your prerogative.

[Foggy_Goggles]

Watch this is you haven't

[MagnificentUnicorn]

I don’t think anyone is opining on what they were thinking. Personally I’d like to know what they were thinking. That’s incredibly consequential terrain in the most stable of conditions.

Personally I would never put myself on that hanging snowfield above cliffs with trees below but that’s just me. I know people have different risk tolerance but there’s really no room for any error or uncertainty on that slope. It’s akin to Russian roulette in my opinion.

I think that objective dialogue about an incident like this is healthy and educational


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[Foggy_Goggles]

I don’t think anyone is opining on what they were thinking. Personally I’d like to know what they were thinking.

Eric was a member of this community. He friends hang out here. If you honestly mean that, go in the ski forum, PM the CB backcountry skiers, and ask them for the contact information for skiers 1,2 and 4.

This is a bit of what I'm getting at. I'm sharing a bit of my emotions. There are plenty of topics to be discussed that can be of value and may help keep people, us included in the future.

How to manage a PWL
What is a Red Flag
Spacial Variability of Surface Hoar
Depth of Snowpack and how if affects stability
Is the a difference between Islands of Safety and Trigger Points
What a common heuristic traps and how to manage them

The Slide Zone is open 24/7 365. Start a thread, drop the knowledge. I'm just asking that you keep, what you would do or conjecture about why this happened to yourself.

Again, it doesn't make me right. Its just how I feel. I didn't know Eric but he is friends of friends. Not a day has gone by since his passing that I don't think about the accident. It just seems like unnecessary piling on to pass judgement and highlight the mistakes you feel they made.

[MagnificentUnicorn]

This is the Slide Zone


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[goldenboy]

FWIW, I started this thread, even as a friend of Eric's, knowing that
a) there was already a really good thread in S/S forum to celebrate Eric
and b) there might be some uncomfortable discussion here in the Slide zone. Piling it on is of course not helpful. Thoughtful discussion is. I've actually wanted to respond to the deeper snowpacks thing above but haven't had the time yet.

[Foggy_Goggles]

Fair enough. I don't need to be right.

I'll try and dig up some information from people way more knowledgeable than me on bridging PWLs, managing instabilities that exhibit wide spacial variability, snowpack depth and how it relates to both depth hoar development and skier triggers and so on.

It's really above my pay grade and I'm not infront of a computer so if any of ya'll wanna get started, let'r rip!

Sent from my Turbo 850 Flatbrimed Highhorse

[goldenboy]

Fair enough. I don't need to be right.

I'll try and dig up some information from people way more knowledgeable than me on bridging PWLs, managing instabilities that exhibit wide spacial variability, snowpack depth and how it relates to both depth hoar development and skier triggers and so on.

It's really above my pay grade and I'm not infront of a computer so if any of ya'll wanna get started, let'r rip!

Sent from my Turbo 850 Flatbrimed Highhorse

No, totally appreciate it and agree that hindsight is 20/20 and some comments weren't all that helpful and very much on the edge.

[muted reborn]

Personally I would never put myself on that hanging snowfield above cliffs with trees below but that’s just me. I know people have different risk tolerance but there’s really no room for any error or uncertainty on that slope. It’s akin to Russian roulette in my opinion.

I'd guess he was gonna jump the cliffs and he probably has done it before and has a nice line through them, I don't see any other reason to be above them, anyone who skis that area agree or disagree with this? Otherwise there are clean lines nearby that avoids that exposure the group would have skied right?

I would be interested in learning about bridging in PWL but on the other hand, I keep things simple. I'm more of a red light yellow light green light guy. IMO after a certain amount of experience the more you know about snow pack doesn't lead to safer decisions it often leads to more dangerous decisions (just an opinion and there are obvious big exceptions to this and my ignorance is showing here). Do I really need to become so confident I can outthink a PWL? This is me talking I'm not saying or implying that group thought this - I'm talking about ME ME ME. Also, frankly, I don't think I'm smart enough to be an expert at snow science.

I would be curious how GB and other locals deal with never ending snow instabilities year after year and still ski fun stuff.

[Darren Jakal]

Maybe chill a bit on the assumptions. It was a tragic accident. Mistakes were made. People are grieving.

Be humble. Learn. Thanks

This is the slide zone where learning can and should occur.

I’m sorry for your loss, but this is the place for a respectful discussion on avalanche activity.

[Foggy_Goggles]

I'm still slacking. I'll try and keep in positive and see if we can stay safe together. It is as much, if not more, about doing than learning. So here is something I can speak to.

The CAIC has been talking about shallow snowpack generally and shallower spot in given lines and slopes as representing increased risk. I think about this in two ways.

1. the less snow between you and the PWL, the higher the probability that you will be the trigger.

2. rocks, shrubs, trees tend to manifest faceting in the snowpack

If you pay attention is the photos of observed avalanches, you frequently see the propagation "connecting the dots" between these features.

[MagnificentUnicorn]

Yes, rocks, krummhoz, trees are not anchors they’re weak spots.

Shallow snowpack is always weaker in general terms.


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[Bunion 2020]

I would be interested in learning about bridging in PWL but on the other hand, I keep things simple. I'm more of a red light yellow light green light guy. IMO after a certain amount of experience the more you know about snow pack doesn't lead to safer decisions it often leads to more dangerous decisions (just an opinion and there are obvious big exceptions to this and my ignorance is showing here). Do I really need to become so confident I can outthink a PWL? This is me talking I'm not saying or implying that group thought this - I'm talking about ME ME ME. Also, frankly, I don't think I'm smart enough to be an expert at snow science.

All relevant thoughts and observations.

Bridging is a Colorado thing. As Dr. K. Birkeland once opined, "Bridging is another term for a slab".

https://www.researchgate.net/figure/...fig7_259509982


Yes, deep enough snow "can" bridge over weakness. Relying on that in times of multiple PWLs is really hanging it out there.

When I was working as as a SS Director I was said to be an expert at judging hazard and mitigating that hazard. Now that I have retired I can look back and see clearly that I was estimating hazard and dealing with that hazard in the way I had been trained. Through the use of explosives for slope testing and following a set of protocols. The biggest danger was me and human nature creating reasons to deviate from those protocols.

I would be curious how GB and other locals deal with never ending snow instabilities year after year and still ski fun stuff.

Same same.

[adrenalated]

I've been trying to wrap my head around the whole "bridging over a PWL" concept for the last couple seasons, especially as I moved from one sketchy snowpack regime (Front Range) to a different one (San Juans). Conceptually it makes sense - it is difficult for humans to impact PWLs buried more than about 1m deep - but putting that into practice in the natural complexities of real terrain is another thing altogether.

In the Front Range it seemed to me like an especially ineffective management strategy as that range sees a lot of wind and snowpack depths tend to vary drastically just across a single slope, especially in the ATL and TL elevation bands. It wasn't uncommon to to slides break across entire bowls with crown depths varying from 1ft deep at the trigger point to 10ft+ in the middle of the bowl. Perhaps difficult to trigger, but unsurvivable if you did. I also rarely saw forecasters talking about bridging as an effective terrain management strategy in this zone, probably for these reasons.

Now here in the San Juans, though we still have a shallow and typically weak snowpack, the snow coverage tends to be a lot more uniform across terrain and various aspects. And here I actually do see forecasters talking about bridging over PWLs, maybe not explicitly in those terms, but they're discussing in nonetheless. For example, from a forecast discussion earlier this month:
"In the Southern San Juans, where the snowpack is over two meters deep, triggering a slide on the January facets seems almost impossible, so we focus more on triggering avalanches on the most recently buried February layer."
So even the forecasters are relying on bridging over the basal facets right now in certain areas in the forecasts and danger rating, which is still a bit foreign to me, I'm used to worrying about them all winter. That said we now have a midpack PWL to worry about so my decision making hasn't really changed and I'm personally not really stepping out into bigger terrain yet.

Which kinda brings me to the question of "how do we deal with never ending snow instabilities and still ski fun stuff." Speaking only for myself here, the answer for me is in the definition of "fun stuff." To a lot of people that means steep and deep and I get that. I personally have a hell of a lot of fun skiing 25 degree pow on ridiculously fat skis. I also got a snowmobile and can go fast and get faceshots all day in zero degree pow. I rarely ski steep or alpine terrain in pow and if I do it's generally late season, smaller storms that are falling on a mostly consolidated snowpack and I'm only worried about surface instabilities. Or, I ski those lines in corn. Or sometimes just in shit snow. All of that's to say, I personally just do not like to fuck with the unpredictable nature of PWLs. There are a lot of people that are willing to push it harder than I am but I've found that the longer I do this, the more and more I'm interested in making consistently conservative decisions.

As Foggy says though, actually making conservative decisions is a lot more difficult than saying that you do it.

[Darren Jakal]

The biggest danger was me and human nature creating reasons to deviate from those protocols.

.

The thing with a Propagating Persistent Weak Layer is the consequence side of the risk equation.

Finding that weak spot in the snowpack that triggers a Propagating PWL more than a metre deep may be a 1 in a million chance.

But the one time it does happen will most likely be a death ride as it will probably be a big event.

[Foggy_Goggles]

https://www.avalancheassociation.ca/...roubled-Facets

How much snow to bridge? It depends. As mentioned, this year we are dealing with the buried surface hoar in addition to the standard. My number is gonna be closer to 2 meters than 1 meter. This is simply because of the snowpack depth variation.

My personal requirement will be a legitimate freeze that cycle and an extended absence of skier triggered avalanches on similar aspects and elevations.

I'm sure this is pedantic but 1/million is a risk I'll take. You only live about 36k days at the most.

I absolutely agree that the consequence profile of the avalanche involving a Persistent Slab weighs heavily in the risk calculus.

[Bunion 2020]

I'm sure this is pedantic but 1/million is a risk I'll take. You only live about 36k days at the most.

Not so sure about 1/million.

In the end that is what it comes down to, people understanding the real risk before you find yourself making a go decision and accepting/rejecting that risk before proceeding.

[goldenboy]

Ok, so my thoughts on deeper snowpacks in a general sense. As mentioned above, at a certain point, they might be considered a bridge, and it's fair to just call that bridge a slab, too. I don't think it's just a CO thing. This year in particular, that entire west had pretty much the same dry spell in late Dec/ early Jan, and it resulted in a pretty similar snowpack (at least that's what I saw as someone who sometimes reads a lot of different forecasts). Utah provides a good example- a few weeks ago they were like "be careful, that layer on the ground is still there!" Two weeks ago, "that layer is dormant and extremely difficult to trigger". And now- nothing, not a mention of it. --Note, that's my paraphrase, not actual quotes.

So what happened? Is it just too hard to trigger now that it's a deep snowpack? Yes, but I'd also say that the same mechanisms that create DH can also create (or is allow the better word?) rounding in a deep snowpack. The vapor gradient (or temp gradient) no longer creates DH, but that nice warm blanket of snow can start to get that crap rounding.

I used the old phone a friend lifeline with a buddy who studied snow in college. Maybe he says it better. Note the last paragraph.
I'd love for some of you expert snow nerds to weigh in, I've always had a much better handle on snow turning into shit than the other way around..

"Mmm, yeah, lots of interesting stuff that goes on here. I'm going to use the term bonding vs healing, because we're talking about this framed with stability in mind.

I think its important to reiterate how facets and DH form, because the same process allows them to get stronger in the end as well.

Crystal metamorphism in snowpacks is driven by the vapor pressure gradient, high gradients mean high crystal growth. We can't measure vapor in the field, but temps actually follow it very close, so this is why we measure temps because we can see what the vapor gradient is doing. Ill use temp gradient moving forward, just know temp is tied to vapor transfer.

Okay so high crystal growth rates are found in large temp gradient and large spaces between crystals. This produces facets, which can develop striations and form large sized cup crystals, depth hoar.

On the other hand, low growth rates produce rounded forms, In alpine snow, low growth rates are usually low temp gradients and high ambient temps. Ground and air temps are close to each other. Less transfer.

So, at high growth rates we get faceted crystals, at low growth rates we get rounding. High growth rates imply high temp gradients, larger crystals and larger pore space with the highest growth rates occurring at high temps at the bottom of the snowpack. Low growth rate implies lower temp gradients (which imply higher ambient temps in the alpine) and small pore spaces.

Our persistence of instability comes from poor bonding with adjacent layers, lack of settlement and strength gain due to an anisotropic structure (angular structure), and cold snowpack temps.

Bond formation between layers and crystals occurs with increasing snow temperatures. So as we start warming up and rounding starts occurring, we see these facets lose their sharp edges and start packing closer together.

For the deeper snowpack, there's two things. First, settlement (associated with a strength increase) is slow in dh layers (and really any persistent layer) due to the angular structure. Weak in shear strength and resistant to vertical deformation (settlement). So it happens as it gets deeper, just slowly. Second, if we bury it really deep, the temp is way lower, so rounding happens."

[goldenboy]

Same same.

I don't know how often I'm just lucky, or how often I "thread the needle" and get it right, since that can be what skiing avy terrain in CO is. Hopefully it isn't all luck after 30ish year of bc skiing.

Mainly, I'm picky in picking my spots. If I don't like it, I revert to riding lifts. And I might even start a separate thread about that because I have some opinions about that.

I don't like skiing sub 30 degree pow. I think it's boring as shit and I'd rather pick lint out of my belly button to be honest. It would perhaps be easier if that wasn't the case. But I'm also not a powder snob. On the contrary, I'm a terrain snob. I fucking love Crested Butte, I don't know if there is another resort in the USA that could keep me this interested after all these years. I love skiing steeps, even if it's chalky snow, not pow. On top of that, Crested Butte works in a way that helps my odds immeasurably. Day 1- storm skiing. Day 2- Phoenix and Spellbound bowls open. Day 3- 3rd bowl and/or Teo 2 bowls open. Boom- I just killed 3 days of a storm cycle and the bell curve of avalanches is now on the downward side, even with a PWL. And I skied a bunch of fun steep terrain doing it. That feels a bit different this year with a more aggressive snow safety director- in the Frank Coffey days nothing would open for days and days. So glad he's gone.

When I do go bc, sometimes I'm playing the aspect game, skiing S during much of early winter. Or it's a good year (as the last 2 have been), and it's fairly green light and you can step out in a lot of places. And I absolutely feel more comfortable skiing in our deeper zone. There's an old TAR where Billy basically suggests that Irwin is more Utah like than CO, given the snow that typically falls there. (It's at 330" for the year vs 200" in CB- pretty typical) Or I might go very little, which has been the case this season. I'm at 71 days lifts, 5 bc.

I'm far from perfect or an expert, but that's how I roll.

[North]

I would be curious how GB and other locals deal with never ending snow instabilities year after year and still ski fun stuff.

Good question. Not nearly enough "year after year"(s) logged to answer with any sort of authority, but I'll at least try to explain my approach.

In the "abstinence" category, 'fun stuff' is relative. I have a snowmobile for low angle roosting, a powsurfer for low angle tomahawking, and a resort nearby with so many nooks and crannies (and rocks!) it would take me a lifetime to sort it all out. All great options for the really spooky times.

In the "pound town" category I feel "never ending instabilities" is overstated and differentiation between manageable (IMO D1 storm slab, D1 wind slab) and unmanageable (PS, DPS) instabilities matters. We have a range that is uniquely snowy for CO with annual snowfall totals approximating an intermountain snow climate (temps excluded), and that helps both in spreading temp gradient (long term rounding) and getting well above the PWLs (shorter term). I don't rely on the former, and try give myself a wide margin on the latter. We also have a shallow zone that exhibits a more typical CO snowpack. I think many would agree the terrain there is more benign, but I avoid it almost entirely due to discomfort with the shallow snowpack. Even on an exceptionally good year like last season, most of the truly sporty skiing happens for me in late March early April.

This question was a good impetus to check myself, so I spent an hour mapping a 2wk period last season (early Feb) where I got out a lot, and compared my terrain choices to the forecasts. I skied 35+ terrain during every outing. PS was listed as possible or unlikely for every outing except the last (not listed). Certainly more exposure to PS than I remembered. The rationalizations would fill a page, so I'll just say that in hindsight I feel comfortable with all but 1 day. I relied heavily on the guidance of an avpro for all days (expert halo anybody?). Still plenty to improve. Good exercise.

Edit to add: we have a really good avy center. They do not rely on an abstinence message, and often detail where the safest options are for 35+ skiing. Their willingness to talk about steep options makes it that much more impactful when they sound the alarm. When CBAC says keep it under 30 I know the shit is truly fucked.

[Darren Jakal]

“I'm sure this is pedantic but 1/million is a risk I'll take.”

It’s hyperbole, so a crap shot. Pick your terrain wisely.

[whipski]

Old and bold skiers

[Foggy_Goggles]

The thing about the crap shoot is that backcountry skiing will always be a risky activity with an imperfect feedback loop. So all we can do is have a hyper awareness surrounding that and understand that we are the eneny.

North and GB, thank for that. That meshes with some of my techniques these days. I used to be out in the backcountry almost exclusively and while I'd like to think that a managed it pretty well, reality is that just by being there during elevated hazard, one sets the decision making bar pretty high. I can enjoy the GFP but the avalanche terrain will always be calling.

Alternate activities, be it lifts, belly button lint or burning dinosaurs works great. Said a different way, it is health an smart to not "have to" go backcountry skiing.

The snow science behind PWLs gaining strength is something I leave to the Forecasters. I understand it but I'm not gonna dig enough snowpits to be the expert. I'd love to know (Lindahl) what your methods and confidence are.

Really it is this spacial variablity thing and how ski cuts, visual observations, hasty pits, full profiles and other tests are at providing any type of valuable data regarding the Go/No Go decision.

It is tough to determine which slopes are supportive enough to ski and which are waiting for you to trigger a large avalanche easily. Consider this in your planning and build a margin for error to account for this uncertainty.

Because ultimately, that is the hypothetical that matters. You've done all the work...cleared the schedule, made the drive, skinned the skin, and there you are. Standing on top of the line. Its hard as fuck to go plan B. You'll fooling yourself it you don't agreed. How many times have you skied down your boot pack? Ever get back to the truck after a full day have made, in essence, zero good turns? Because that can be backcountry skiing. I you have to embrace that. If you can't, you need bigger margins.