Tell me what ya know about ‘em. Trying to become an expert in understanding them. It seems to be the most fickle, most necessary to get in the field and just them in real life.
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Tell me what ya know about ‘em. Trying to become an expert in understanding them. It seems to be the most fickle, most necessary to get in the field and just them in real life.
These avalanche.org pages are pretty good overviews of most avalanche problems you'll see in a forecast. https://avalanche.org/avalanche-encyclopedia/wind-slab/Quote:
Originally Posted by thejongiest
In short respect them big time...by the time you figure out its too late its really too late.
From my own experience, windslab in itself is not the danger. The danger is in what is below and what slope angle you are on. Here, in the Canadian Rockies it typical to find lots of wind affected snow. Some is bombproof because it is consistent right to the underlying base, but a lot will be over a basement of depth hoar. Bridging becomes the issue.
Windslab combined with a propagation layer is a no go for me. If you have ever experienced a massive collapse of a propagating layer under a thick slab you would understand the kind of energy that is in play. It sounds like a gunshot.
That’s my 2 cent.
Thanks for some info, that makes sense. What about when wind slabs get buried? Do they bond well with the snow above/below? Or they just sit there? Does the interface cause facets to grow?
It’s complicated. If it was sensitive to collapse before it will remain so until conditions allow for rounding of the facets. It’ll be basically invisible too with fresh snow on top. Surface hoar can form very quickly on calm clear nights, so new snow might be lying over surface hoar over the slab and whatever is under thatQuote:
Originally Posted by thejongiest
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It’s complicated as mentioned above. Snow metamorphosis depends on snow depth and outside temperature (the temperature gradient). With new snow the depth is increased and the gradient may improve, but not if it stays cold enough for a gradient greater than 1 degree Celsius per 10 centimetres of snow. With the cold and shallow snow depth, sublimation and deposition will continue and facets will be created. If the gradient is less than 1 degree per 10 cms of snow then rounding and necking will start to happen and the snowpack will start to strengthen.
As mentioned above, buried surface hoar can also come into play when new snow is deposited, but other interface conditions can also be present.
There is an idea that layers deeper than a metre may not be affected by the weight of a single skier. However, this can lead to danger if you happen to find that shallow spot and break through to the facets below. That’s why it’s better to avoid the thin areas around rocks where some will think that it is safer because the rocks will anchor the snow. It’s counterintuitive to think it’s safer out in the belly of the snow slope where the pack is deeper and the gradient is better and (hopefully) the bad layers are buried too deep for a skier to trigger them.
Hope this helps.
I would add that if you’re skiing the belly of the slope to avoid a persistent slab problem, you’ve got bigger problems. I get that it’s safer sometimes but without history in the area and on that slope it’s a gamble that I will usually avoid
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Yep, as I stated above, propagating and persistent layers are to be avoided period.
This is for everyone who thinks skiing trees is safe from avalanches.
Hard to see in my crappy photo, but there's an avie fence on the trees. And nobody would put one there unless they where worried snow would slide. https://uploads.tapatalk-cdn.com/202...055d9752df.jpg
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Holy shit, I have no idea wtf this thread is about.
Lol.
To add some more info, I was skiing this weekend and on Saturday we noted some serious windslab across a slope and while it wasn't propagating it was definitely hardening up and pretty deep. Then we went back on Sunday and a bit of sun and a bit of warming totally transformed that windslab into hot consolidated pow. Amazing what 12 hours can do.
For the sake of being practical, wind slabs are just like any other layer or snow/weather event that may cause instability. How likely that wind slab is to bond with the snowpack, and/or initiate and propagate a slide is dependent on a variety of local, complex factors, other posters here do a good job talking about some of those factors.
When I am making decisions, a wind slab is just another potential problem in the snowpack. They are very common because mountains in general are windy places; winter storms are usually windy to some degree. How much of a problem a slab is is why stability tests are helpful for gathering data about the strength of the slab, and how it has or hasn’t bonded with the snowpack. In general, windy events are concerning. Mountains are windy places so I assume the slabs are all over the place unless I know otherwise.
To the OP: you mention wanting to be an “expert” at windslabs. In the interest of safety, you will get a lot more bang for your buck becoming an expert on how you make decisions and choose terrain. From personal experience, it is more about terrain selection than understanding idiosyncratic details on the snowpack. Hope that is helpful.
Definitely and coming back around to this the last 2.5 months I've really gotten out much more frequently and in different conditions. And I think what I was getting at earlier is really something that just comes from experience. Seeing different kinds of wind affected snow and how reactive it is and how the mountains I know tend to setup is the kind of IRL experience that's really necessary.Quote:
Originally Posted by safetymeeting