It sounds like you don't think conditions are any trickier than usual. Is that right?
Read my first post in this thread. There is clearly a generalized instability affecting the Alps, Jura, Vosges and Massif Central from quite low altitudes. Currently a time to play it safe.
The thing is, lots of years we warn of a dangerous avalanche situation developing then nada but the stopped clock (me) is right this year.
Yes. I think some dodgy layers may have been there for a good while (unless you think they would have transformed since?). I remember going for a walk on some of the first snow (my photos say it was 18th October). It was a sunny but cold day and on the south facing parts (circa 2500+) the snow was huge crystals crunching under my boots. I remember hoping it would all melt away before the seasons snow started building up on top of it.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
The article suggesting that we are having almost 3 times more accidents then average for last 20 years.
My friends were riding a line that would have been one of my first choices on that day had I not been with the large group. The Couloir they were going into had slid two days before - theoretically making it a safe option- but they had to cross a pocket of snow to get to the entrance. This is what slid, I have never seen it slide on that scale in my whole time in Verbier.
Everything has changed and we have lost a friend.
to follow up on what Xavier dela Rue said, this is something I noted on the first page of this thread
Quote:
Now people often ski couloirs on higher risk days because they auto-purge their snow and are relatively safe but this kind of couloir is exactly the type not to ski because the entrance is a big funnel that accumulates snow. It is a configuration that comes up time and time again in avalanche incidents.
Coming back to the accidents this season. In France we've had 2 or 3 winters of relatively benign conditions so a winter with a widespread avalanche risk, even in mid mountain areas, comes as a bit of surprise for people. 2 deaths in the Bauges, 1 in the Jura and 1 in the Chartreuse and 1 in the Vosges the last few days. These are traditionally mountain ranges that people ski when the avalanche risk higher. A heuristic trap as both 1 of the Bauges avalanches, the Vosges avalanche and the Chartreuse avalanche occurred on slopes known for their avalanche risk.
@davidof, Cheers. Interesting the incident where the guys were taken and inflated their air bags but were buried by a secondary slide.
@AndAnotherThing Check out the Mikael Bimboes vid of his avalanche adventure for a skiers eye view of getting buried by a second wave after the airbag has saved you from the first.
http://youtube.com/v/D6dEBgrQp0Q
I did some English sub-titles for it in case it's hard to follow their French (you have to turn that on to see them)
Anyway, the vid is seriously alarming as his Gopro keeps going after he is buried and records his voice. You also hear the genuine pacnic in the voices of his companions on the hill. It's a few years old but hits home.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
@Ed_sec, what is also quite alarming is that he doesn't appear to have learned his lesson (it was him & his crew who triggered the Suisses bowl earlier this winter - video did the rounds a few weeks back...).
After all it is free
After all it is free
@davidof, I would propose that couloirs auto-purging of snow is a fallacy and a heuristic trap to some extent. Yes very often they do have this particularity, but then it is also so dependant on the 'set-up', and given the very peculiar start to the winter we have had on so many fronts it beggars belief the places people are heading to...
I always try to keep in mind (and god knows over the years I have had my share of dodgy decisions and close calls etc) the Saulire couloirs in Courchevel which get skied to mogul fields and bombed to death and yet still occasionally go off BIG after the right sequence of events (fortunately mostly with the assistance of a bomb from the pisteurs in recent years...) they may not be comparable to other more enclosed couloirs but adequately prove the point for me.
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offpisteskiing wrote:
@Ed_sec, what is also quite alarming is that he doesn't appear to have learned his lesson (it was him & his crew who triggered the Suisses bowl earlier this winter - video did the rounds a few weeks back...).
@offpisteSkiing Not surprised. They seem to represent the more gung ho aspects of skiing and indeed the one in the vid was triggered by him dropping some distance onto the top of the slope. Luckily I'm at an age where I have no wish to emulate them even if I could!
Hope the eyes are sorted btw
Ski the Net with snowHeads
Ski the Net with snowHeads
@offpisteskiing, I think of the Saulire couloirs more as small valleys myself. This is what passes for a couloir around these parts
but yes, taking the statement that "couloirs are safe on high avalanche risk days" is a heuristic trap but clearly one that is popular and of course if you are in that couloir when it purges it is not a great place to be.
Last edited by Ski the Net with snowHeads on Mon 25-01-21 19:16; edited 1 time in total
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
davidof wrote:
@offpisteskiing, I think of the Saulire couloirs more as small valleys myself.
Snob
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
With couloirs, there are two scenarios.
The planning stage, and on the hill. When figuring out where to ski on a sketchy day I don’t usually think this is the day to head for a steep couloir, but I have chosen to ski one when navigating my way out of a potentially unsafe situation. Finding yourself on a mountain side that might go, going for a bit that’s already gone provided its not feed by real estate ready to slide can be the best option.
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
@offpisteskiing I found the vid of what I assume is the Suisses bowl avalanche they triggered. Your opinion of their efforts seems to be shared as the most liked comment to that Vid on YT was this:
Comme pas mal de commentaires écrit avant le mien, je pense qu'il serait pas mal d'éviter de dire que cette vidéo est réalisé avec des professionnel de la montagne. Il n'y a rien de professionnel a partir tous en même temps dans une pente, expose aux avalanches et qui doit l'être de nombreuses fois dans l'hiver, peut etre meme prevu au PIDA juste pour faire jolie a la vidéo. Le "t'as un dva c'est bon" est un mensonge que vos dizaine de milliers de viewers vont penser être la vérité.
Bref des erreurs qui peuvent couter cher. Je suis pour la liberté de nos montagnes, faite ce que vous voulez peu importe ce qu'il adviennent de vous, c'est votre choix, ca me dérange juste qu'on rabâche les règles de sécurité a longueur d'hiver pour voir des vidéos comme ca. Nous somme entraine a venir vous secourir, nos chiens aussi. Mais s'il vous plait, ce qui lisent mon commentaire, apprenez les bonnes conduite a tenir et prenez juste ces belles videos pour de la fiction.
One just has to hope that the gap between what these FWT guys do and what us average skiers (me not you) do is obvious enough that we do indeed regard their exploits as fiction.
But when they go for a play with their pals in places we can all go to like this then the lines get blurred.
You know it makes sense.
You know it makes sense.
Ed_sec wrote:
@offpisteskiing I found the vid of what I assume is the Suisses bowl avalanche they triggered. Your opinion of their efforts seems to be shared as the most liked comment to that Vid on YT was this:
<snip>
Yes and that ties in with what Simon said above about heuristic traps.
The comment you found is from Tom Lesuire, who is a pisteur at Val d'Isere as well as being a pro freestyler so knows something of what he is talking about. Same for Simon (offpisteskiing) who most people know.
Anything I may say is just a commentary and shouldn't be taken as a recommendation or otherwise.
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
@Ed_sec, Watching your video above I was going to note how 'hard' they were on the snow pack from the off.
The modern "InstaReady" freeride style with big drops and slash turns puts a lot of energy through the snowpack. More so with 5 riders at a time. Not falling doesn't cut it these days....
Poster: A snowHead
Poster: A snowHead
@AndAnotherThing.., Not falling would be a good start for me
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
@Ed_sec, At least you have a snowpack to fall on. Grass and sheep poo is mostly what we have here
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
@AndAnotherThing..,sheep poo sounds less slippy than bouse which works not bad ......
I note the comments about a lot of those being caught are experienced locals. In my observation such people look at the terrain in a totally different way too professionals like patrollers and guides. The locals main focus seems to be on what are going to be the best lines for enjoyment and the professionals are looking at the hazards. Also the attitude that "I've been doing this for years so I must know what I'm doing" it may be that they have been getting away with it for years and developing bad habits and following advice from others with similarly flawed ideas.
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Ed_sec wrote:
@AndAnotherThing Check out the Mikael Bimboes vid of his avalanche adventure for a skiers eye view of getting buried by a second wave after the airbag has saved you from the first.
.
Holly f--k : After an incident like that I would be embarrassed to post...
Instead they made a vLog.
Think about the x3 factors (snow, people, terrain) and they are clearly all wrong in multiple ways.
For starters...
Snow - clearly high risk (cat 3/4) on day after fresh snow
Terrain - Steep and rocky. 35+ degrees.
People - Skiing it as a party line all at once
Text book example of exactly how not to do it!
Last edited by Anyway, snowHeads is much more fun if you do. on Mon 25-01-21 23:30; edited 1 time in total
@Haggis_Trap, It was pretty textbook as you say with over-familiarity being a key factor. As he says they go there all the time and never think twice about it. " It didn't let go before" etc.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
Sarge McSarge wrote:
I note the comments about a lot of those being caught are experienced locals. In my observation such people look at the terrain in a totally different way too professionals like patrollers and guides. The locals main focus seems to be on what are going to be the best lines for enjoyment and the professionals are looking at the hazards. Also the attitude that "I've been doing this for years so I must know what I'm doing" it may be that they have been getting away with it for years and developing bad habits and following advice from others with similarly flawed ideas.
.
I partly agree but its mainly as Bruce Temper stresses in his book, a numbers game.
After all it is free
After all it is free
Sarge McSarge wrote:
I note the comments about a lot of those being caught are experienced locals. In my observation such people look at the terrain in a totally different way too professionals like patrollers and guides. The locals main focus seems to be on what are going to be the best lines for enjoyment and the professionals are looking at the hazards. Also the attitude that "I've been doing this for years so I must know what I'm doing" it may be that they have been getting away with it for years and developing bad habits and following advice from others with similarly flawed ideas.
There are slides going in all directions and on slopes that are not the typical trouble spots. Everyone is a bit freaked out by it. Another big dump coming with wind is likely to exacerbate the problem.
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It doesn't seem to be as bad as Switzerland or France but here in Austria we have had a few avalanches too and the snow pack is far from ideal.
https://lawinenwarndienst.blogspot.com/
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
DB wrote:
It doesn't seem to be as bad as Switzerland or France but here in Austria we have had a few avalanches too and the snow pack is far from ideal.
https://lawinenwarndienst.blogspot.com/
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
@BobinCH, thanks for sharing that. Very heavy listening but very important...
You know it makes sense.
You know it makes sense.
jbob wrote:
Sarge McSarge wrote:
I note the comments about a lot of those being caught are experienced locals. In my observation such people look at the terrain in a totally different way too professionals like patrollers and guides. The locals main focus seems to be on what are going to be the best lines for enjoyment and the professionals are looking at the hazards. Also the attitude that "I've been doing this for years so I must know what I'm doing" it may be that they have been getting away with it for years and developing bad habits and following advice from others with similarly flawed ideas.
.
I partly agree but its mainly as Bruce Temper stresses in his book, a numbers game.
Or as Mark Twight says ''White stuff kills'' and ''never fall off ice'' in his opening statement in the alpinist bible. It is all about human factors in the decision making process.
Thanks and yes very heavy listening.
His parents much be going through hell at the moment.
Poster: A snowHead
Poster: A snowHead
I am trying to get to grips with the properties of the persistent weak layers that are oft discussed and have a question for the wise with a lot more knowledge than me.
The pwl (or owl in predictive text ) is often described as collapsing like dominoes leading to failure in the slab over it etc etc, so I am assuming that the crystals are arranged in a vertical fashion on end which would allow for this sort of collapse. However I am a little confused as to what shape the crystals are and from my limited reading so far there seem to be a number of different shapes - needles, feathers, wedges and cups are mentioned.
It is the cup shaped ones that I am struggling with and they seem to be the most prevalent.
In my simple mind a cup shape is a relatively stable design. If you place a teacup upside down (is that the configuration in the pwl?) then it has both stability , resistance to toppling and a degree of compressive strength so I don't understand how a dominos effect can occur. For sure there will be little resistance to shearing forces (a teacup will easily slide on a flat surface) and I get that little bonding will take place but beyond that I am at a loss.
Any input gratefully received - I have obviously oversimplified what is a complex science but any explanation on my level would be appreciated.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
^ my advice - don't over think the snow science or physics.
the weak layer can be any type of snow (ice, powder grains, hail stones, hoar frost) that doesn't bond to a layer of windslab above.
the most common / dangerous weak layer is caused by hoar frost. this is the sugary layer that coats surface of snow afters several cold clear nights.
see picture below - imagine the kind of frost that might form by condensation over time on a freezer door.
now : the very bottom of snowpack is always 0C (as snow is a great insulator).
so you really only need to worry about 2 processes... rounding and faceting.
rounding : if the air temperature is close to, or above, 0C the new snow crystals will over time turn into rounder shapes which bound together better.
especially if there are freeze / thaw cycles.
faceting : if the air temperature stays cold (<0C) then new fallen snow crystals can turn into facets / hoar frost.
this is the weak layer, pictured below, that can cause problems if subsequently buried by slab.
the rate of faceting depends how deep the snow pack is.
a shallow snowpack in cold weather has biggest temperature gradient so produces facets / hoar frost faster.
Have a read below (from a friends blog).
However best advice is not to over complicate the snow-science!
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
@snowheid,
My limited understanding is they are just crystals with very little structure strength or bonding. I've never really thought about the exact reason for their shapes but a quick google search reveals cups come from depth hoar.
The important thing is irrespective of shape they don't bond - it's like having a sugar layer(s) in a victoria sponge. If you tilt it up and put pressure on the top face it will eventually slide. The shape of the crystals doesn't change much. At a certain angle e.g. 50 deg+ it won't hold without any additional weight. At a very low slope angle it's much less likely to go (e.g. 20 and below). There is however a range where it is most likely to go with a bit of additional pressure - (e.g. 30 to 45 Deg).
Whereas one skier/boarder may not be enough weight to trigger a deeper layer on the same or on a different slope, the weight of the snow from a small slide can cause a chain reaction.
If the floor in a building collaspes it can take out the floor(s) below because of the weight, in this case only one floor was weak but a dominoes effect was triggered. The straw that broke the camels back as it were.
Often these layers are being supported at the bottom of the slope where it runs flat. If an avalanche takes out the support layer from another layer of snow that will give too. An avalanche at the end of a U-shaped valley could cause all the valley sides to go.
As others have said I wouldn't put too much thought into how/why it is formed, there are people who spend their lives doing that. I'd concentrate more on reading the avalanche report and being able to identify the areas of danger highlighted in the avi reports (Avi level, aspect, slope angle, elevation etc)
Last edited by Well, the person's real but it's just a made up name, see? on Tue 26-01-21 12:59; edited 13 times in total
My experince with it, is when we have been in the Alps high altitude, on the slops with little snow, there was hard crust on top, you brake the crust, then there was empty space like 20 cm of air and loose sugar on the ground. Imagine 60cm of fresh snow on top of that crust, scary.
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Quote:
... is they are just crystals with very little structure strength
Exactly - all types / shapes of faceted snow can be dangerous.
However because they are formed by a temperature gradient they will always be arranged vertically.
The weight of new snow (or a skier) can they cause eventually this vertical arrangement to collapse - resulting in an avalanche.
Google "weak layer snow" for some typical images.
I am trying to get to grips with the properties of the persistent weak layers that are oft discussed and have a question for the wise with a lot more knowledge than me.
The pwl (or owl in predictive text ) is often described as collapsing like dominoes leading to failure in the slab over it etc etc, so I am assuming that the crystals are arranged in a vertical fashion on end which would allow for this sort of collapse. However I am a little confused as to what shape the crystals are and from my limited reading so far there seem to be a number of different shapes - needles, feathers, wedges and cups are mentioned.
It is the cup shaped ones that I am struggling with and they seem to be the most prevalent.
In my simple mind a cup shape is a relatively stable design. If you place a teacup upside down (is that the configuration in the pwl?) then it has both stability , resistance to toppling and a degree of compressive strength so I don't understand how a dominos effect can occur. For sure there will be little resistance to shearing forces (a teacup will easily slide on a flat surface) and I get that little bonding will take place but beyond that I am at a loss.
Any input gratefully received - I have obviously oversimplified what is a complex science but any explanation on my level would be appreciated.
Also Bruce Tempers research, but this is more detailed. It is not the be all end end all of subject matter books though, but just one a lot of people have come across.
Also there are plenty of online resources available.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
Thanks for all the replies. I should say that I do have enough practical experience to interpret avi reports and apply it to terrain when I am out in the mountains and also understand what a weak layer is (btw@Haggis_Trap, that is a cracking image you posted which shows the layer in detail) but I was just curious as to how the cup shaped crystals worked. A bit of further investigation seems to indicate that they grow into columns a bit like balancing a number of teacups on top of each other upside down which makes a lot of sense as you then have an inherently unstable formation.
After all it is free
After all it is free
@snowheid, I think it isn't so much the cup shape (except that they don't have branches to interlock with each other) but rather that the thin layer of large, loose crystals prevents the layers above and below bonding to each other.
Last edited by After all it is free on Tue 26-01-21 15:41; edited 3 times in total
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
Haggis_Trap wrote:
Quote:
... is they are just crystals with very little structure strength
Exactly - all types / shapes of faceted snow can be dangerous.
However because they are formed by a temperature gradient they will always be arranged vertically.
The weight of new snow (or a skier) can they cause eventually this vertical arrangement to collapse - resulting in an avalanche.
Google "weak layer snow" for some typical images.
The problem is that such phenomena can be hidden by a layer of fresh snow. And this threatens an avalanche. Experienced skiers may recognize instability in snow cover, but beginners can definitely get into trouble.
FAQ
Poster: A snowHead
......
with a lot more knowledge than me.
) is often described as collapsing like dominoes leading to failure in the slab over it etc etc, so I am assuming that the crystals are arranged in a vertical fashion on end which would allow for this sort of collapse. However I am a little confused as to what shape the crystals are and from my limited reading so far there seem to be a number of different shapes - needles, feathers, wedges and cups are mentioned.
