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Thread: Wind Slabs

  1. #1
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    Wind Slabs

    Tell me what ya know about Ďem. 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.

  2. #2
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    Quote Originally Posted by thejongiest View Post
    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/

  3. #3
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    In short respect them big time...by the time you figure out its too late its really too late.

  4. #4
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    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.
    Last edited by Darren Jakal; 12-09-2022 at 05:22 PM.
    All conditions, all terrain.
    Expect nothing, donít be disappointed.
    Too Old To Die Young (TOTDY)

  5. #5
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    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?

  6. #6
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    Quote Originally Posted by thejongiest View Post
    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?
    Itís complicated. If it was sensitive to collapse before it will remain so until conditions allow for rounding of the facets. Itíll 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 that


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  7. #7
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    Itís 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. Thatís why itís better to avoid the thin areas around rocks where some will think that it is safer because the rocks will anchor the snow. Itís counterintuitive to think itís 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.
    All conditions, all terrain.
    Expect nothing, donít be disappointed.
    Too Old To Die Young (TOTDY)

  8. #8
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    I would add that if youíre skiing the belly of the slope to avoid a persistent slab problem, youíve got bigger problems. I get that itís safer sometimes but without history in the area and on that slope itís a gamble that I will usually avoid


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  9. #9
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    Yep, as I stated above, propagating and persistent layers are to be avoided period.
    All conditions, all terrain.
    Expect nothing, donít be disappointed.
    Too Old To Die Young (TOTDY)

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