The rain expected to 2000m could stabilize conditions at lower altitudes, esp. if it gets refrozen but things will be sketchy higher up. Watch the freezing line and amount of snow that falls and read the bulletin. The snow-pack is very mixed at the moment, sugar snow, transformed snow, windblown at the entrance to couloirs and ridges, ice crusts. It is very heterogeneous and the avalanche bulletin may not capture all of the subtleties we will see Christmas week and beyond.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
Very dodgy here too.
Is it wrong to be hoping for rain/a heatwave?
If something dramatic doesn't happen, it's going to be dodgy for a while.
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?
edit to reply to Peanuthead:
If there are weak layers within this thin snowpack, such as depth hoar at the very base they can stay for the whole seasons. Essentially meaning that the whole snowpack could slide at anytime, especially as new weight is added each snowfall. Light cold fluffy snow is good in that it is "light", but sometimes a damper heavier snowpack can be good to help weighten the snowpack and allow layers to consolidate. (i think, davidof can help).
Yesterday I saw very hard packed top layer of about 10cm's thickness resting on top of a large layer of graupel sand like snow. that sandlike snow is weak, and just waiting for that thicker layer to move, especially once it has more fresh weight ontop. Also if it is very cold when it snows, the new snow won't bond to the hard layer very well, creating another perfect sliding surface.
Hi davidof, is posting not allowed on your site anymore?
I don't like that comparison to 2005.
I have been worried for a long time about the next snowfall. Of course we all want snow, but the ammount and size of surface hoar that has been around for several weeks is scary.
Aswell as what is mentioned about the huge temperature gradient, there are going to be various layers, not just soft. There will be hard compacted layers from the strong winds back at the beginning of the month.
What will happen to this surface hoar once it's buried? Am I right in thinking that it will stay, but could be compressed out so to speak?
And what do we need to help the snow pack? Mild conditions when it snow's so that the layers can consolidate? Lots of snow to try and get a deep snowpack so that the temperature gradient is smaller over a bigger area and thus allowing layers in the middle to potential strengthen.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
> What will happen to this surface hoar once it's buried? Am I right in thinking that it will stay, but could be compressed out so to speak?
If enough snow falls, say a meter dump or more, it will more or less bridge the weak layer so that a skier crossing would have difficulty triggering a slide but you do see crownwalls of 2 - 3 meters at times. If it rains then refreezes it will bond the layer, this is what may happen at lower altitudes over the next few days. Otherwise wait for the Spring thaw. .
There has been increasing chatter amongst guides over the last few days here in France and I expect Switzerland and they are concerned about the developing situation. Amongst the victims in 2006 were guides, pisteurs and rescue workers. The amount of snow we see is critical. Of course it could go 2006/7, little snow until March and a low number of fatalities.
It has been a very stable start to the season even where there is a lot of snow. Just watch the bulletin closely in your area to decided when and where it is safer to ski off piste.
Olic, I'm in the process of migrating the old accounts, PM your email so I can check?
After all it is free
After all it is free
Had a mate who is a guide based in La Grave pop round here (Serre Chevalier) yesterday, and he too said it's going to be extremely dangerous with these snow falls on the current base, be it the hard frozen pack of the bare ground.
In a bizarre way, this lack of snow currently that we have down South and then the snow that is forecast is going to make the week long European Avalanche course I' doing Jan 5 quite pertinent according to Per as there's going to be some interesting facets to investigate and demonstrate.
Last edited by After all it is free on Wed 18-12-13 9:29; edited 1 time in total
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There was some amazing surface hoar development in the Three Vallees last week. Really big crystal growth with night after night of calm conditions, and in shady places getting on for 10cm deep. Scary.
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Just watched that Henry's vid above, in the background think his clients might have been touring for the first time
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An avalanche in Lech yesterday is reported here and may be related to the conditions being discussed in this thread.
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.
Please don't get me wrong with this reply. I'm not contradicting, just questioning, as I'm keen to get replies that help me with my own understanding - which may be wrong!
OliC wrote:
Light cold fluffy snow is good in that it is "light", but sometimes a damper heavier snowpack can be good to help weighten the snowpack and allow layers to consolidate.
So a ton of feathers is lighter than a ton of bricks? I had imagined that a ton of fluffy snow weighs pretty much the same as a ton of damp snow. Then you see the slow 'sharks teeth' glides going off in the spring, I had not imagined that the snow had somehow gotten heavier (though certainly more dense) but that its moisture content had grown to the degree that it was better lubricated to move against grass / rock slabs, etc. Like I said in my opening remarks, read this as a "have I got this right, or am I a slightly confused person?"
Quote:
What will happen to this surface hoar once it's buried? Am I right in thinking that it will stay, but could be compressed out so to speak?
I thought that both surface and depth hoar can be pretty persistent. But if you do get, say 2-3 metres on top of a layer of surface hoar, would that not alter the temperature gradient between the ground (zero degrees) and the top (minus whatever) to make it a very shallow temp gradient, which will promote sintering within the entire pack? And make it more stable... eventually.
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
It's the 'eventually' that's the problem. Who's going to wait a fortnight after a dump to get fresh tracks?
You know it makes sense.
You know it makes sense.
davidof, So, if a metre of snow falls over next say 2 weeks (which seems reasonably likely), we should be in good shape?
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
bobski62 wrote:
I thought that both surface and depth hoar can be pretty persistent. But if you do get, say 2-3 metres on top of a layer of surface hoar, would that not alter the temperature gradient between the ground (zero degrees) and the top (minus whatever) to make it a very shallow temp gradient, which will promote sintering within the entire pack? And make it more stable... eventually.
If the grains are facets (small cup like crystals) then removing the temperature gradient will mean they slowly transform into round crystals which will bond with a freeze-thaw cycle or melt water. Add a temperature gradient back in and they will start the transformation process again to facets then hoar crystals (gobelet or large cup like crystals). So yes, a 2 meter dump will mean the facets re-transform into round grains and bond. However the reverse process is slow, it is like you can boil water in a microwave very quickly but that water will stay scolding for a good while once you take the energy away.
However the temperature gradient(s) in the snow-pack is rarely even, it can be different in different layers of the snow pack, particularly across crusts where there may be a strong temperature gradient over a few mm of snow which is almost impossible to measure. You can then get facets forming on the crust causing avalanche instability. Some of these weak layers, particularly above crusts, can be almost impossible to see.
Yes, 2-3 meters would be a good thing in one go now although I wouldn't want to be in a mountain village or ski area when it happened to be honest. We look to be getting 30cm + 20cm + ??? which is a bad thing, making the snow pack more complex. Oh and in between these storm cycles we are going to get some nice sunny weather.
Depth Hoar is the final state of the transformation and these crystals will not change even if the temperature gradient is removed. They can be stabilized by rain or by melting due to thawing. There is (almost) always a layer of hoar at ground level. What we've seen in Henry's and my video are facets.
Sintering is where the original crystal shapes (stars) etc break down due to mechanical action, first into smaller particles then into round grains which can fuse through a freeze-thaw cycle producing a stable snow layer... which of course can then change into facets and hoar if there is a temperature gradient.
Here is a picture of a slab sitting on surface hoar (frost) that I took, it is surprising how much weight those fragile crystals can take.
Even fresh snow can form an unstable layer esp. if it is very cold at the start of the storm. We should see the opposite tomorrow - warm turning colder which is a more stable situation.
Thinking back to 2005/6, the instability remained in the snow all season. I remember my local ski resort spent the day in early April doing extensive avalanche control work and they got large slabs to trigger on all the slopes they tried except those to the south. The kind of slabs a group of skiers could trigger if they were on the slope.
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Poster: A snowHead
davidof, to cut to chase, how easy or difficult will it be for reasonably competent guide to keep his/her clients out of trouble in coming weeks? ie would you expect most responsible guides to make it uneventfully through the season notwithstanding the dodgy situation now, or will any any individual guide need to be lucky to avoid any trouble?
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
peanuthead wrote:
davidof, to cut to chase, how easy or difficult will it be for reasonably competent guide to keep his/her clients out of trouble in coming weeks? ie would you expect most responsible guides to make it uneventfully through the season notwithstanding the dodgy situation now, or will any any individual guide need to be lucky to avoid any trouble?
To be honest, nearly everyone will make it through the season but the people most at risk will be locals (like me) who are tempted into the mountains when it is particularly dangerous and to a lesser extent, guides. Locals may have the feedback of hundreds of trips where nothing happened in what look like similar conditions and guides have to work and they only have their expertise to keep them safe; which is does, 99.99% of the time. Visitors who have any awareness of the conditions tend to either: not risk it off piste or they hire a professional.
It will be interesting to see how things develop over the next week. Henry makes a good point:-
Quote:
if we get the 20-40 cm or more of fresh snow that is forecast over the next week, many steep slopes with fresh snow will be unpredictable in that dozens of people may be able to ski the slope before it is triggered by someone. All of us will be assuming that most steep slopes with fresh snow could release at any time even if they have tracks already on them.
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?
Hi davidof, thanks for your input. I'm happy that your overall understanding is consistent with my overall understanding! Though I think we differ on some of the subtleties of sintering. Not for now though, another time. "Chapeau" to a guy who tours as much as you do and is still alive! And, btw, many thanks for "pissed whores" (sorry!) - though not quite used to the new format yet...
Picking up on your points above, if it goes on like it has so far, I can see myself having fun in the lower woods and gentle <30 slopes a lot this year.
This is fascinating stuff! Thanks a lot to all of those who have taken the time to explain things so clearly on this thread.
A question if I may - how localised will these conditions be? If I'm reading this correctly it's the prolonged cold that's been causing a lot of the problems. Where I'm off to for new year in Austria is quite a bit lower and has been reporting freeze thaw conditions for a while now, but it looks like there might be some significant snowfall just before I arrive. Is it likely to have the same issues as Val with regard to the snow pack?
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Quote:
If I'm reading this correctly it's the prolonged cold that's been causing a lot of the problems.
^ Keep the snow science simple.
The only 2 processes you really need to know about are facetting and rounding
In very simple terms....
Facetting : occurs when it is stays cold and dry for long period of time. Crystals appear on the surface of the snow pack. These are the weak layers of sugar snow which can be dangerous once covered with a new layer of wind slab / snow.
Rounding : occurs when it gets a little warmer or the snow pack gets much deeper (thus reducing the temperature gradient within the snowpack). The crystals turn back to rounder snow flakes and start to bond properly again. Over time this results in a more stable snow pack.
The problem at the moment is that the weak layer of faceted snow is buried. Its meant to stay cold so this layer of weak snow will not consolidate very quickly back into stable snow. Potentially the buried weak layer will remain dangerous for a long time OR until the alps get a good freeze thaw cycle. The best thing to reset the snow pack would be rain to 3500m followed by a refreeze
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
11 degrees in the Rheintal at the moment,,,,, DO IT! RAIN!
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Just heard from a mate who's in a bit of a state driving to me here in Serre from Hinterlux, that the family who were tragically caught in that Lech avalanche, the father was a good friend, they climbed the Matterhorn together this summer along with others raising a substantial amount for charity.
It's affected my mate badly as he takes his son with him off piste a hell of a lot. Going to be a somber though provoking session tonight!
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Weathercam, sounds horrendous my heart goes out to all friends and family.
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I'm sorry to hear that Gavin.
As a final thought. Nothing will give me greater pleasure than zero avalanche injuries or fatalities at the end of the Christmas Holiday period. Either because I have completely misjudged the situation or because they've made good route choices and decisions based on the avalanche bulletin, advice from professionals, training etc.
I hope everyone enjoys their holidays, gets to ski off piste and tour and has excellent snow.
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Quote:
"Chapeau" to a guy who tours as much as you do and is still alive!
OK, I think this needs to be kept in perspective. There are risks, it can be dangerous, sure. You are still more likely to die driving to or from the trail head than you are when you are out skiing [source]. The wording in that report is a bit odd, but they differentiate between touring (they call it backcountry) and lift-served off-piste (which they call it off-piste). Their figures show touring is safer than off-piste, which they attribute to greater awareness of snow conditions amongst those who go touring.
EDIT - Of course, that doesn't change the main issue, conditions now look very worrying indeed. A very useful but sobering thread indeed.
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.
I don't think those conditions are prevalent everywhere, and in fact I would never make generalisations that one mountain is safe or dangerous and another is not.
Aspects of mountains can be vastly different, however it is good to be reminded about the dangers all the time.
I wouldn't ski off piste unguided unless I had a strong mountaineering background and a lot of winter experience.
After 20 years in mountain rescue I'm still very cautious and always try and get local advice when skiing somewhere new.
Today in Avoria it was raining down to 1400m roughly, and snowing above
+3 to 5 in the valley.
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
Been snowing all day in La Plagne.
Steady trickle. Nothing major. Maybe 5cm.
But staying cold (and not the sleet that many sites forecast)
You know it makes sense.
You know it makes sense.
sah wrote:
Quote:
"Chapeau" to a guy who tours as much as you do and is still alive!
OK, I think this needs to be kept in perspective. There are risks, it can be dangerous, sure. You are still more likely to die driving to or from the trail head than you are when you are out skiing [source]. The wording in that report is a bit odd, but they differentiate between touring (they call it backcountry) and lift-served off-piste (which they call it off-piste). Their figures show touring is safer than off-piste, which they attribute to greater awareness of snow conditions amongst those who go touring.
EDIT - Of course, that doesn't change the main issue, conditions now look very worrying indeed. A very useful but sobering thread indeed.
Quite!
Also the bizarre question about whether most guides will be lucky to make it through a season unscathed! If the job was that dangerous no-one would want to do it, and there would be little point in hiring one!
We're not talking about skiing on Mars without oxygen!
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
Conditions will definitely be interesting after the fresh snow. The avalanche category for Chamonix tomorrow is 2/5, but I think that will depend on how much snow falls tonight. The forecast is also for high winds so there could be extensive slab too. It is possible that the bulletin has underestimated the level of risk. Let's hope that it's actually the Met Office that has overestimated the amount of snow and wind.
I've been working on avalanche safety courses the past five days and have found a lot of poorly bonded snow. The pack is very thin, hence the temperature gradient has been steep. This has caused facetting within the pack. It is simply too early to say what will happen, but I think it's fair to say that being extra cautious would be a good move.
Stay safe out there folks
Poster: A snowHead
Poster: A snowHead
Quote:
davidof, to cut to chase, how easy or difficult will it be for reasonably competent guide to keep his/her clients out of trouble in coming weeks? ie would you expect most responsible guides to make it uneventfully through the season notwithstanding the dodgy situation now, or will any any individual guide need to be lucky to avoid any trouble?
This is a very relevant post and one that is bringing up some real concerns that exist amongst the skiing community. I have already had a query from a client concerned about the possible avalanche risks for a course in 3 weeks time. The next few days will be critical as we evaluate the changes that will take place in the snowpack as the present warming conditions along with significant rain have their effect on the lower slopes. As the report says, you will do well to note the freezing level and changes in the pack with altitude as well as aspect.
Thankfully, whilst snowpack stability is not an exact science and there is still a lot to be learnt, our understanding has significantly improved and risk assessment is no longer in its infancy. That luck will be the key factor in a guide or off piste instructor avoiding trouble is far from accurate. I spend the majority of my time taking clients off piste and I can assure you that I would not be doing my job if I relied solely on luck. This is the exact time to enlist the services of a guide or experienced instructor - you will stay safe AND be able to ski the best that the mountain has to offer. Mountain professionals are watching the present situation keenly. This historical information along with evaluation of current conditions all allow guides and instructors to choose descents wisely.
Please keep the posts and links coming in. They can only help to add to the formation of the overall picture of the snowpack. This information is an incredibly valuable resource.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
Groan. Note to self: must use more smileys. It was meant as a light-hearted remark. Hey ho.
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?
Meteo France has upped the risk level to High for the Oisans (la Grave, les Deux Alpes, Orcieres, Puy St Vincent) and Aspe/Ossau in the Atlantic Pyrenees and Hautes-Pyrenees. The Prefecture in the Atlantic Pyrenees has issued a special warning of the risk of skier triggered slabs above 2300/2400m noting "the snowfalls on Thursday has radically modified the stability of the snowpack".
Meteo France estimates the risk as considerable above 1700/1800 meters in many other ranges including the Belledonne which has seen the brunt of the fresh snow with 40cm falling above 2000m. Surely an error for this range where the risk is more likely to be High, it is a dangerous massive with mountains rising to 3000m and many large, avalanche prone bowls, the mountains take the brunt of atlantic storms moving across France. Coupled with its proximity to Grenoble and Chambery is is popular with a large pool of backcountry enthusiasts.
davidof, thanks for your updates and advice. Especially when you have such critical observations or opinions that may be at odds with official bulletins or not well emphasised in official bulletins. With time I understand more and more complexity of avalanche prediction and I think anyone going out there, guided or unguided, needs to understand all the dangers.
Would be fantastic to see this thread as an ongoing thread on snowpack similar to the weather outlook thread, maybe made into a sticky
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
peanuthead wrote:
davidof Would be fantastic to see this thread as an ongoing thread on snowpack similar to the weather outlook thread, maybe made into a sticky
While I think it is a good idea to give a general warning of conditions I really think anyone considering going off piste is best served by consulting the avalanche bulletin for their mountain range and then speaking to professionals such as the piste patrol if they are in resort.
As Diverskify says above, if in doubt, hire a guide or instructor experienced with off piste. Henry Schniewind's blog for Val d'Isere is a good source of information. Follow Henry Schniewind @HenryOff_Piste, Andy Perkins @andypmtnguide, Simon Christy @offpisteskiing, Alison Culshaw @Offpisteperform, Simply Savoie @SimplySavoie and me (@davidzof) on Twitter for some local beta.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
davidof wrote:
guides have to work and they only have their expertise to keep them safe; which is does, 99.99% of the time.
That suggests a problem for every 10,000 days' off-piste skiing. So if there are 100 days in a season, one in 100 guides will have an incident. I hope it's rather more like 99.9999% of the time, or even more.
Interesting though. Last year the worry was snow falling onto unfrozen ground in early December. "Nobody knows what will happen as we've never had so much snow like this before." This year the worry is snow falling on frozen ground. I think that proves there's always something to worry about.
After all it is free
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James the Last wrote:
davidof wrote:
guides have to work and they only have their expertise to keep them safe; which is does, 99.99% of the time.
That suggests a problem for every 10,000 days' off-piste skiing. So if there are 100 days in a season, one in 100 guides will have an incident. I hope it's rather more like 99.9999% of the time, or even more.
Interesting though. Last year the worry was snow falling onto unfrozen ground in early December. "Nobody knows what will happen as we've never had so much snow like this before." This year the worry is snow falling on frozen ground. I think that proves there's always something to worry about.
It was just a figure, I'm not a six sigma expert or anything.
Still lets take the figure of 1600 French guides with 5-10 killed in any season and your figure of a 100 day season (on average for all guides). That gives us a 99.999967[1] chance of a guide dying in a mountain incident on any day of the season for 5 guide deaths per year or a a 99.997% chance of being killed in any one season (taking the lower figure of 5 guide deaths).
[1] This is better than the six sigma rate of 99.99966 and bare in mind that it includes accidents where guides are not with clients so on a guided day you are almost certainly safer.
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bobski62 wrote:
Groan. Note to self: must use more smileys. It was meant as a light-hearted remark. Hey ho.
That's the trouble with the internets, no one knows what you mean, only what you say. I'm afraid I may be guilty of taking things a bit too seriously sometimes which is cardinal sin on a forum, but with the recent deaths in Lech and the dreadful coverage (e.g. BBC said "there was an avalanche warning issued that day" - true but misleading as it was level 1) I am rather keen to see facts more plainly stated. Sorry if I jumped down your throat unnecessarily.
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Quote:
Last year the worry was snow falling onto unfrozen ground in early December. "Nobody knows what will happen as we've never had so much snow like this before." This year the worry is snow falling on frozen ground. I think that proves there's always something to worry about.
2011/12 saw November snow on warm ground in what was a very mild autumn which caused all the full depth avalanches when spring came but it was a largely favourable situation wrt to skier triggered avalanches
2012/13 saw late October snow (about a meter and a half) which all melted by mid November (as PamW always notes) then considerable snowfall in December on cold ground giving a generally stable avalanche situation. However the winter persisted into April and the very long season, from October to June with a very wintry March led to a small overall increase in avalanche fatalities in France.
Personally I wasn't too worried in either of the last two seasons. The risk was fairly well defined during the periods of snowfall and a day or two afterwards.
FAQ
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