 Poster: A snowHead
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Fork of this discussion --> https://snowheads.com/ski-forum/viewtopic.php?t=147999&start=840#3485928
So the big accidents like the CAF one will skew the figures when comparing year to year. What's more interesting is to know if there were more incidents (and only fatal incidents are more or less reported 100%) and how serious they were.
If you are writing an article for your site you may also consider the more widespread use of airbags to be a factor, perhaps the (tête sous la neige) figure gives a hint to that and avalanche education but I'd wait for a longer term trend. The French press were talking about the effects of avalanche education today but the big driver is almost certainly weather - either stable conditions and/or poor weekend weather keeping the warriors at home or on safer routes. At the start of the 2017/18 season there were a few big local names who got killed and that did seem to lead to a bit of calm afterwards.
Still big upsurge in touring up and down pistes around here this season, damn nuisance they are when someone could break a trail just to the edge of the piste and avoid any danger of collision. At the 7 Laux there were huge caravans heading zig zagging across the open ski runs!
BTW RIP Alexia Casado, first ski fatality in France this season. She was a sports studies student in Chambery, University of Savoie killed at Val Thorens after a severe fall.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Well it's blowing a hooley in the valley as I type this and getting blown up against the windows are loads of little snow pellets that were once flakes and now have been bashed into oblivion by the wind.
On a couple of the big buildings near us I can see big cornices building up on leeward side of the rood with some chunky slabs, so up the hill it's going to have to be treated with extreme caution and respect.
Might take a pic of the building me thinks.
Anyway the purpose of the post is that some of you might have seen the pictures below from Serre Chevalier after the big snowstorm of December 1st and the impact of the various controlled (or not) avalanches, some that went according to plan and others that did not 
The image is of particular interest in that the fracture line is nigh on 750m long as it goes out of shot, and like the first image, on the other side of the ridge this sector was not due to open for a couple of weeks, so no real danger to the pistes.
Last weekend when some of the lifts opened once up the mountain it was a similar story with nearly all slopes above 25% having been blasted the hell out of.
So a question to others who have been out in different resorts, have any of you witnessed similar activity ?
In talking to a highly respected La Grave guide of over 30 years who regularly is on the morning commission run to determine if the lift should open, he too can't quite work out what the strategy was, as all it has done is expose nigh on bare ground that will be the bottom of a weak layer, especially with the current conditions happening.
And he said that they should have waited at least three or so more days for the snowpack to settle, which it obviously has done as there are no visible natural slides that have occurred?
We will shortly be interviewing the head of Piste Mountain Security to try (which will be delicate) to find out if new protocols a la the US (where they too bomb the shite out of everything) are now in situ, I did ask said guide if he wanted to attend, but he thought it might not be cool
So again, has anyone else witnessed a similar scenario, i.e Verbier ?
So will be interesting and if you can think of any questions you'd like asked then let me know.
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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?
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The problem you appear to have in the frontier zone is the start of a persistent weak layer (aka the "guide" killer) - that will then hang around all season and be triggered from time to time by people going off piste or touring.
You had a similar situation in 2016/17.
To give an example http://www.data-avalanche.org/listAvalanche/1492276335389
this slide went on a weak layer formed in the autumn.
These big avalanches that you've seen are typical of a homogeneous weak layer formed in the snowpack early in the season. That layer may get deeply buried and reactivated later in the season, say with a thaw as melt-water percolates through. The slabs are hard to trigger with explosives once buried. A resort really doesn't want one of those kind of slides reactivated by skiers during say the winter holidays when the pistes below are busy.
Last edited by Well, the person's real but it's just a made up name, see? on Fri 13-12-19 23:54; edited 3 times in total
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@davidof, as I said we've never seen activity such as that and to the extent, and without the blasting there now would not be a perceived weak layer, it does seem to be a new protocol or using other terminology, initiative
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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| Weathercam wrote: |
| @davidof, as I said we've never seen activity such as that and to the extent, and without the blasting there now would not be a perceived weak layer, it does seem to be a new protocol or using other terminology, initiative |
Why would there not be a weak layer?
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@davidof, not too sure what point you're trying to make?
As I said we've never seen triggering in resorts of this magnitude, and there's no relation to ANY NATURAL activity occurring like you mention in 2016 / 2017 so would seem prior to yesterday everything is/was reasonably stable.
Per, who I'm sure you'll agree knows his stuff, he's already skied LG top to bottom twice this season, and is running the training there next week, is concerned that they've now created a situation, as after the blasting we had numerous cold clear nights, where the new snow along with transported snow will not bond as well to the base layer that was left as if they had not done the blasting in the first place, and let nature take its course, and then blast.
And again without sounding like a scratched record, they have NEVER carried out so much control, so our question is, is this a NEW PROTOCOL a la USA?
We're meeting head honcho next Tuesday, and as I type this the sound of blasting is echoing around us.
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| Weathercam wrote: |
So again, has anyone else witnessed a similar scenario, i.e Verbier ? |
In Verbier they bomb extensively after fresh snow to secure the pistes and itineraries. Also the main routes get eavillly skied so you usually only have to worry about the last dump.
I would have thought the weight of the snow would eventually break/bond a deeply buried weak layer?
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| Weathercam wrote: |
| @davidof, not too sure what point you're trying to make. |
There is a weak layer in the snowpack along the French/Italian border, that layer is not going away and they don't want avalanches coming down on lifts or open ski runs so have done control work. I'm sure they always do control work, after all the ski lift avalanche was triggered by gazex - clearly they were right to trigger that given the size of the slide. Maybe the slides are bigger than you've seen before but you've only been overwintering for a few years.
I mean your photos speak for themselves.
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| BobinCH wrote: |
I would have thought the weight of the snow would eventually break/bond a deeply buried weak layer? |
Water percolating down in the spring will disturb the weak layer, as will snow creep during the season, as will skiers. This type of slide is very big and very random. I guess they triggered the chair lift avalanche, saw the scale of the problem and then bombed the other areas in the PIDA.
I suspect the situation is different over in la Grave.
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| BobinCH wrote: |
| ... I would have thought the weight of the snow would eventually break/bond a deeply buried weak layer? |
It depends on that layer. In BC you can have early-season events which can put a weak layer low down in what's a very large snowpack. If it's the right type of bad news then it never goes away all season. Sometimes people find it hard to accept that what look like good runs can't be used for the entire season.
You would be correct I think in suggesting that the effects of any deep layers are likely to reduce over time. Digging pits all the way to the ground (a rule in some places I ride) is a good way to check.
I don't know the statistics, but presumably sometimes they stabilise and sometimes they don't.
Late season climax avalanches are a bit different I think, where the pack breaks at ground level.
Unless they're practising, I doubt any resort would spend money on ordinance without having thought through what they're doing and why. The guess that they're nailing a weak layer sounds reasonable to me. You can't do that in the back country, hence you can be hamstrung all season, but at a resort the terrain is more limited so taking out a risky layer before it causes trouble is probably a very sensible approach. Those photographs both show areas which look to either threaten lifts or what looks like a piste... hence they're controlling the risk.
The intent here is presumably to clear a known weak layer now, before it hurts someone. They can't be trying to prevent future weak layers forming which would be impossible. If there's an immediate new layer, then that's arguably bad forecasting, but it's not going to be very low, and can always be banged away later. The repeated use of explosives is common: it's not a one time thing unless the snow cooperates.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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After a good morning thrash around trying to stay one step ahead of the game (weekend warrior groups) we called it a day and descended back down to one of the establishments at the bottom where I bumped into a ESF instructor/guide I know of a similar vintage to me, cut a long story short he said all the slides were natural and happened on the Monday 2nd, and I explained that might be why I did not hear anything, though probably I can't hear the gazex going off - he said that they've seen activity in areas where they have never ever seen anything go.
Then 30 mins later we have to move seats as we are only drinking and end up sitting next to my old neighbour, another ESF instructor/guide who is with a Serre Che pisteur, and his version was that it was déclenchement, but that they had no idea that it would propagate into such massive slide(s).
So numerous theories from a whole bunch of people who actually know and ski the mountain inc Per the guide, and no doubt on Tuesday I'll hear some more from the boss man.
But I'd surmise that once they used the gasex and that whole face went, along with the other big one near the Prorel they then decided to blast the hell out of everything.
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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.
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Pretty crazy on the mountain this weekend, would seem loads of people had a ABS for their birthday, and many waling from the car park with their triggers on!
A very large number of interlopers as well, numerous FreeRide groups from other resorts/regions and many Italians.
I did one run being very cautious after a ridge hike taking a sensible line, but behind me were two people, one with no pack etc
Very soon after the lift giving access to that area was closed, so not too sure as to the reasoning but temps were getting warm.
And then I read this, one group caught and the guy not wearing any transceiver.
https://www.ledauphine.com/faits-divers-justice/2019/12/14/hautes-alpes-un-skieur-hors-piste-enseveli-par-une-avalanche
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Massive avalanche in Col des Mouches in Verbier. Steep East facing slope. 2 metre crown. Probably triggered by bombing on Friday or Saturday when the area was closed.
Not much other activity visible. You can see the bomb home to the right of this small one on Mont Gele (closed today)
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You know it makes sense.
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| BobinCH wrote: |
I would have thought the weight of the snow would eventually break/bond a deeply buried weak layer? |
Correct : though snow needs to be about 1.5-2m deep to naturally compact previous weak layers. Up until then the extra snow is just extra load (so there is no easy answer to your question).
Looking at Serre Chevalier photos I can see point Per As making. Triggering avalanches to ground early season makes snow pack thinner. Thin snow pack has higher temperature gradient so more likely to contain future weak layers. Though how they manage terrain in La Grave very different to Serre Chevalier (easier to shut lift in LG for 3 days if snow best left to settle)
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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Poster: A snowHead
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Big skier triggered avalanche in the Clot Gauthier at Serre Chevalier on Saturday- 2 meter deep crownwall. That's why they control the stuff above the pistes and ski lifts. It's in the PIDA.
HT> though snow needs to be about 1.5-2m deep to naturally compact previous weak layers
what do you mean by that?
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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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?
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| Weathercam wrote: |
| @davidof, again scary stuff, |
Well I guess they just opened so there is a bit of a powder frenzy. No harm done in this case but obviously any in resort slide can give the piste patrollers, volunteers and other rescue workers extra work if they suspect anyone is underneath. That slide is a beast though, huge amount of debris at the bottom, you could be killed outright, somewhere where an airbag would be good, if you have time to use it.
Clearly the frontier zone from the Haute-Tarentaise to the Haute Maurienee to the Montgenvre / Serre Chevalier sector is very sensitive at the moment and will possibly be throughout this season. Someone was caught at Valloire and avalanche control work is producing some very big slides.
It is no where near as sensitive in the Isere despite the headline risks being the same (4 at the weekend). There was some windslab on ridgelines on Thursday with a couple of smallish skier triggered avalanches - which is one reason I didn't climb the final pitch I was touring.
You've clearly got a lot of interesting subjects to discuss with head of piste services.
Last edited by Well, the person's real but it's just a made up name, see? on Mon 16-12-19 14:28; edited 1 time in total
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@davidof, I'm drawing up the questions now, but will be delicate as he might feel under pressure etc it's a tough job for sure.
One question is, on a drag lift that gives access to some terrain that is far more suspect than Clot Gauthier face (Eychauda drag) why do they not limit people skiing to those with equipment, but now I fear that many people now have all the gear and no idea etc, like I said, seemed that everyone had an ABS bag for their birthday this year, and yes I will come clean about my little incident in the forest!
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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| Weathercam wrote: |
Like I said, seemed that everyone had an ABS bag for their birthday this year |
Yes it seems that way. At the point where i turned back on Thursday there is a big 200 meter climb up a huge open slope. A couple of guys passed me "unclip your trigger, if this goes, it goes big and you'll need your airbag". I like the gung-ho attitude. The rucksacks looked new. I decided not to hang around to see if it was "going big" although I don't think the danger was huge - although someone got a whoumph on the more windloaded side of the slope, he turned back.
Because we have a huge student population you can see all the new intake up in the resorts at the weekend with their just purchased kit - or at least crying in the car parks as they examine the skis they've just ripped the a*rse out of on the barely concealed rocks "my skis, boo hoo hoo, 900 feckin euros worth boo hoo hoo, ruined!" Well yes, I do feel their pain.
Other things the student population do are:
1. stop their car in the middle of the road when they see snow, but it is well known that the local students run round on bald tires and don't have chains (but still have ABS and the best skis).
2. stop the second they reach the carpark blocking everyone behind while they look for a space despite there being an empty car park 50 meters further on - as if some concierge is waiting for them "oh grungy students, we've been expecting you, let me park your car somewhere convenient, carry your skis and maybe wipe your **se for you"
3. stop at the turnstyles blocking the lifts because they are waiting for Old Dingo who is sparking up a foul roll-up a few meters back
oh and to keep this "on topic" the old "one beacon between two technique" - that's even worse than the ESF giving the shovel to the "man" at the back.
Then there are the old guys who want to lift the safety bar 100 meters out from the station right 100 meters above dead skier gulch.
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@davidof, dead skier gulch
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One man killed in Kleinwalsertal yesterday. Touring on the Ifen, our local mountain. Buried under 3m snow. They found him after ~1 hour. Not sure whether he was carrying a beep or not 
https://vorarlberg.orf.at/stories/3026284/
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One dead out of Park City Utah on Sunday.
https://utahavalanchecenter.org/avalanche/48826
Elsewhere reports say:
"... found by two passersby after being buried for at least 25 to 45 minutes. Two individuals came across the avalanche debris field and saw a snowboard sticking out of the snow...
These individuals dug him out and immediately started doing CPR. The man died of his injuries after being taken off the mountain."
Refering back to some of the discussion above, the early report says:
"Weak layer is likely the old October and early November facets acting as a persistent weak layer. Graupel-pooling below the cliff-band is also possible. This is to be confirmed..."
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You'll get to see more forums and be part of the best ski club on the net.
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Interesting topic and fascinating thoughts on Persistent Weak Layer. It strikes me the phenomenon of PWL is the ultimate work of the devil when considering snow stability.
I'm sure we have all read various gurus on the subject with slightly differing takes.
Deep in my memory I recalled a movie clip which illustrates perfectly, to me, the toxic nature of PWL.
I apologize for not being able to bring a "link" into this text (weak IT skills) However take a look at FWT Journal 2015 EP9 Some explanations after Julien Lopez avalanche in Kappl.
This is found on you tube.
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| davidof wrote: |
HT> though snow needs to be about 1.5-2m deep to naturally compact previous weak layers
what do you mean by that? |
PWL needs to be buried by > ~1.5-2m before weight of the new-snow will naturally compress the weakness and make it safer.
Up until that point each new snow fall simply adds more weight / risk.
Freeze-thaw can obviously also stabilise snow-pack.
However a deeply buried PWL may need major temperature fluctuation.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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| Haggis_Trap wrote: |
| davidof wrote: |
HT> though snow needs to be about 1.5-2m deep to naturally compact previous weak layers
what do you mean by that? |
PWL needs to be buried by > ~1.5-2m before weight of the new-snow will naturally compress the weakness and make it safer.
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The snow depth will have a damping effect on the skier or other trigger on the surface rather than "compressing the weakness" - if you dig down you'll see the weak layers are still there in the snowpack. That's why you get crown walls like this
Not much compression there.
Of course you rarely, if ever, get an even coat of snow over the side of the mountain. Some areas will be wind scoured, some areas more snow be deposited. So you end up with maybe 2 meters in one place where an elephant could ski over and 50cm on a roll over and bam, you've just triggered that weak layer you thought was buried.
The persistent weak layer is, by its very nature, persistent. The temperature fluctuation for it to go will either be the layer melting at the end of the season or rain that percolates down and then refreezes - say below 1800-2000 meters.
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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.
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When I was on that course a good few years back digging loads of pits*, what was interesting was to see the difference in six or so pits dug by all the students in more or less the same area, there was absolutely no logic at all some of the time as to where the weak layers were, some tap tests were classic whilst others the snow did not budge.
Met up with the Dir of Pistes and Security yesterday, his way of assessing/dealing with the snowpack is very very different to how a mountain guide might view it, basically bomb the hell out of it asap.
Whereas a guide would prefer 5 snowfalls of 20cm he'd prefer a 100cm in one hit.
And the detail as to the incident of the avalanche that engulfed the Cucumelle chair was/is as I suspected something that will never really come to light even after direct questioning, the stuff of legends 
The other big slide under the Grand Serre, that was caused by the vibrations of a piste basher!
I'll be writing it all up shortly.
*Just below P2 in La Grave on that nice E/SE'ly facing slope.
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| davidof wrote: |
Not much compression there. |
^ Actually in that photo the bottom weak layer is obvious.
However "something" has reduced its thickness on right of the photo.
I would guess that giant slab was likely triggered by a weaker "hot spot" located further downhill from the crown wall ?
Subsequently releasing the entire slope.
As you observe - that is the classic problem with PWL.
It takes exceptional sequence of weather events (like heavy rain followed by re-freeze) to flush them out of snow-pack.
Even then the snowpack across an entire mountain is never uniform.
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You know it makes sense.
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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They are fairly sure that people were caught in it. Looking at the video there are certainly people on the piste that got covered. Doesn't look good!
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Poster: A snowHead
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Pisteurs not doing their job.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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@Whitegold, wot? Do you ever not talk shite?
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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?
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You need to Login to know who's really who.
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Moment of impact.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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You'll need to Register first of course.
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@BoardieK, he had a beacon. And thankfully turned on. He also had a pocket of air so I suspect either an avi bag that deflates (like a jetforce) or very very lucky.
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I also suspect Recco, not a transceiver. You would think he would be found much more quickly if he had a beacon, unless his friend didn’t have one and they waited 5 hours for rescue to come.
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You'll get to see more forums and be part of the best ski club on the net.
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@Steilhang, I often don't agree with @Whitegold, but as the Andermatt avalanche came across an open piste he asks a valid question, albeit in the format of a statement.
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@chocksaway, the Andermatt avalanche was not a slab, but rather a 'Gleitschneelawine', i.e a glide avalanche which is not possible to predict, and which does not let itself be controlled by usual methods such as dynamiting.
As it turns out, they got lucky. Only two people injured, and four others got caught but managed to free themselves.
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FAQ
