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  1. #26
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    Quote Originally Posted by LeeLau View Post
    Very closely spaced trees can serve as anchors. Trees with foliage that grows right to ground are actually better anchors then trees without vegetation. Generally speaking trees have to be close together enough that fast tree-skiing is difficult for the trees to be good anchors.

    Widely spaced trees are not good anchors and can actually serve as weak points in the snowpack. They're also things to hit if you get swept downslope in an avalanche -- as you recognized.

    So, as with almost everything to do with avalanches ... it depends.
    Another point about trees - they are also indicators of avalanche history. While they should not be used as a sole point for decision, they can be used to identify whether a slope routinely slides.

    Generally speaking - no trees can indicate regular slide paths; small trees can indicate occasional slide paths and large trees generally only grow in rare/unusual slide paths or slide free areas.

    For example, a buttress ridge with large growth timber is usually a safer bet than two open slopes on either side. Trees will be absent from those slopes for a reason.

    That brings out another point about avalanche safety - - while an avi course is essential, experience and personal knowledge must be added. The ability to read a slope - where the slide paths are, which ridges hold the lowest danger - can be gained with experience in the mountains. The ability to know a slope, and know the history of that particular slope - can be gained with experience in a particular area.
    Living vicariously through myself.

  2. #27
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    Mar 2006
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    thanks for the great knowledge-sharing, guys. I really do appreciate it.




    a safe and happy season to everyone!

  3. #28
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    Quote Originally Posted by bookem View Post
    Daffern also makes the point that the distance from snow surface to a weak layer may be less near terrain features (trees, rocks) which rise above the snowpack. A fracture can then propagate through to deeper areas that may have otherwise been unaffected.

    I am nowhere near experienced enough to say whether this is actually practical knowledge, i.e. that you should choose lines away from trees and protruding rocks.
    Actually a good practise is to shy away from areas of thin snowpacks. I would speculate that people in the Rockies or continental snowpacks are more alert about this then people like myself in coastal snowpacks. I mention this because your sig indicates you're from around this area.

    Thin snowpacks breed facets and facets are dangerous. From a practical point of view, that means that if I'm in area with a thin pack, I'll tune down the aggression level - whether or up or downtrack. To give you a better concrete example, this weekend i was on a windy ridgeline trying to figure out where to ski. I went over to a rocky outcrop to look and probed. The snowdepth was 90cms. I skinned over to a more open slope and probed. The depth there was 240cms. Both slopes had windslab and were pretty wide open and about 34 degrees. I skied the slope where the start zone had more snow.

  4. #29
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    Jun 2006
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    We have so many choices with our fatty snowpack and neverending ranges of peaks. I like to look at westerly aspects sometimes when conditions are likely to be scary in a lot of places. Not that windslabs can't happen atop windward slopes.

  5. #30
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    Quote Originally Posted by Conundrum View Post
    There is a lot of stuff to ski even with a moderate danger rating. I might be fisting the dead horse here, but a good Avi I course would cover this topic really well.
    Wow.
    That's an interesting manglage of metaphor.
    . . .

  6. #31
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    Another great thread from LeeLau.

    Carry a clinometer & know the slope angles.

    Choose the low risk line for the ascent.

    Windward exposures will not have as much loading re: new snow, but will be thinner snowpack re: faceting. It is a trade off.

    Approach suspect terrain from above w/cornii drops & ski cuts.

    While descending, ski cut convex microterrain features & pause to watch for any results.

    Beware terrain traps, look for the ridges, not the gullies, nibble the edges, avoid the bold centerpunch line if not certain (that one has saved me).

    One at a time, safe place to safe place & CLEAR THE RUNOUT.

  7. #32
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    Oct 2002
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    A quote comes to mind regarding high slope angles and their consequences. I'm pretty sure its from Hanscom and Kelner's Wasatch South Guide. Slab avalanches tend to be rare on extremely steep slopes (45-50+ degrees). But then again, you have a whole other set of hazards to deal with.

    I think line selection comes down to the big picture. This isn't all about skiing, and this isn't all about avalanches. Ski touring is travel in the mountains, and a broader view of you and your place in the mountains is a good way to stay safe. Furthermore, ski touring isn't at all about death either, despite the rough times being experienced in a lot of communities this year. Its about living! As someone said above, look for safety, not for hazards.

  8. #33
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    Dec 2006
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    ask yourself... what am i connected to? to simplify Bill H.'s post. watch for tension points such as rocks and trees and breakovers, although rocks and trees can also be safe havens. do your reading.

  9. #34
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    For me a good thing to do is think about fluid dynamics. If its going to slide what might happen, where might it happen? think about gravity, transitions and loading.

    What's the run out like (as far as your decent is concerned)? terrain traps? cheese gratters or strainers (rocks, cliffs, and trees)? How comfortable are you with taking that ride? Further more if your comfortable with the ride then are you comfortable with your partners and the depth you might be burried? Are there escape routes? would rescue be possibe with out putting your partners in danger?

    I think that all of those are factors to be added in after being concious of what aspects are safer and more prone.

    I also really like to factor in the feelings I recieve through out the day as I walk in fresh snow (and test it when possible) and see how it's reacting.

    Going up can be just as dangerous, a proper up track is deffinately important also. Always keep in mind you can break the tension from below.

    As far as being in a clear valley with a cloudy alpine this could be a dangerous sittuation if you aren't aware of your surroundings it's probly best to wait for another time.

  10. #35
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    Ridges are generally always safer than an open slope with a continuous pitch.

    Also, in the PNW, you can find crazy terrain variations within a single slope. If I'm skiing something steep, I generally try to find a spine of some sort, with various fall lines. Sluff will fall off but a wide spread fracture is unlikely. Also, if one aspect of the spine/ridge does break you at least have a chance that the other aspects remain in tact.

    You see people do this all the time on the big mountain lines in AK:


    Last edited by altasnob; 01-14-2008 at 07:41 PM.

  11. #36
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    Quote Originally Posted by LeeLau View Post
    The first day after a big storm event with high winds. Nice weather is forecasted. I'm set to go with a friend of mine who's also quite motivated and want to ski some N faces.
    What makes those north faces so appealing? Lack of sun effect? Windloading?

    In general, I think the lust for immediate post-storm powder turns in any specific location should be immediate cause for concern.

  12. #37
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    this thread is why it is worth it to stick through all the summer crap

  13. #38
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  14. #39
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    Quote Originally Posted by RootSkier View Post
    What makes those north faces so appealing? Lack of sun effect? Windloading?

    In general, I think the lust for immediate post-storm powder turns in any specific location should be immediate cause for concern.
    They're big, aesthetic, clean, faces that usually get windloaded. After thinking about it more and talking to my friend I decided to take my summit fever tendencies out of the equation and not going. Those faces will be there later.

  15. #40
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    Seems pretty thorough here. I think it's worthy to note again that just because a slope has trees doesn't mean it's anchored. As LeeLau said, if you can ski through the trees fast, they probably aren't tight enough to anchor the slope.

    I'm not an expert on digging pits, but this is something I picked up from my avi class, maybe others could chime in on their opinions of this:

    One thing I thought was interesting from my Avy 1 class is that a pit should be used to decide not to ski something rather than to decide to go forward with skiing a slope you are nervous about.

    By that I mean (4 scenarios with digging a pit):

    1. If you're sketched out by a slope, getting a good result from a shear test shouldn't make you change your mind and think the slope is safer. (I think this one isn't always obvious to people)

    2. If you think the slope is pretty safe, and the shear test is bad, it might make you change your mind and think the slope is less safe.

    3. If you think the slope is safe and the shear test is good, it's possible you are good to go with skiing the slope.

    4. If you are sketched out by a slope and the shear test is bad, it should be obvious that you shouldn't ski the slope (almost left this one out because it seems common sense)

    I think my instructor's main point here was to use your observations and smart travel decisions first, then add the pit as a last piece of the puzzle. If you are already skeptical about stability, it's probably best to turn around than use a pit to make yourself feel safer about the slope. Pits are more useful if you dig one in a similar place over a period of time such as in the same area at a similar aspect every week or two and you look at the progression of the snowpack as new snow piles up. You also want to pick the slope/aspect you are likely to ski. Digging a pit on a slope/aspect taht is not representative of what you are skiing is not really helpful. The instructors mentioned some studies that were done making snowpits all over the same slope and getting pretty variable results from the pits.
    Ride Fast, Live slow.

    We're mountain people. This is what we do, this is how we live. -D.C.

  16. #41
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    good points by JT. Our instructor said that he only rarely digs pits. His point was that a pit only shows you the conditions at that exact point.....go 15 feet further in any direction and the conditions could change. Echo what JT says, use a pit as a piece of the puzzle but not the whole piece.

    It truly sucks that the death this weekend spurred this thread, but glad to see that something positive has come of those horrible events.

    Nice that this thread is free of the name calling and bashing that the other thread has become.
    ROLL TIDE ROLL

  17. #42
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    Quote Originally Posted by shirk View Post
    This has been posted before but it's a good watch. Some tips on the human element as well as terrain management.


    A Dozen More Turns
    Thanks for the link, I hadn't seen that before.

    Great thread.

  18. #43
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    Quote Originally Posted by montanaskier View Post
    Great points.....the Avy class we took earlier this year was great, lots to think about. I would add that having an escape route in case something does go wrong. Skiing the sides of a route instead of the gut, thus making it a bit easier to perhaps bail if need be.
    It's been said elsewhere in the thread, but this one is a tough call since triggers such as shallow buried rocks, etc. are usually on the sides of a chute, with the deepest snow being in the middle. My training taught me to look for the most uniform shot w/o obstacles or variations (triggers).

    Anyone else care to elaborate?

    Good shit boys let's keep it up!

  19. #44
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    Dec 2004
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    765
    Rocks on the side of chute are anchors- you are the trigger.
    Skiing right down the middle of a loaded area is the worst place to be unless you are ski cutting and bailing to a safe zone.

    Anchor to anchor, safe zone to safe zone.

  20. #45
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    I think there is room for both to be true situationally.

    Rocks and small trees can be nearly or shallowly buried objects that affect the structure of the snow through the temperatures they hold and the associated gradients that can come from a warm tree or rock and colder snow or air adjacent to them. They can be trigger points when they dot across a starting zone. In a lot of early season slides you can sometimes connect the dots and see how they influence stability because slabs tend to fracture along them.

    On the other hand, if you want to have an escape route, skiing the edge of a track below a starting zone and even in one does provide you with a rapid exit into terrain that may not be affected by the slide. Thin spots there may or may not be trigger points depending on the structure of the snowpack between them and the starting zone.

    I believe if you are in a situation where you think you need to ski the middle of a slope because it is safer than the sides, you are *probably* shaving your margin of error pretty close to begin with. That might be a signal to reevaluate your decisions and perhaps choose a lower angle less exposed line.

    I boiled my thermometer, and sure enough, this spot, which purported to be two thousand feet higher than the locality of the hotel, turned out to be nine thousand feet LOWER. Thus the fact was clearly demonstrated that, ABOVE A CERTAIN POINT, THE HIGHER A POINT SEEMS TO BE, THE LOWER IT ACTUALLY IS. Our ascent itself was a great achievement, but this contribution to science was an inconceivably greater matter.

    --MT--

  21. #46
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    Quote Originally Posted by alto View Post
    As someone said above, look for safety, not for hazards.
    Reminds me of...We don't ski the trees, we ski the spaces between them! Awesome, words to live by!

  22. #47
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    Bumpage again

  23. #48
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    Nice Bump.

    FWIW - I don't believe this was around at the time of the original thread. A lot is very basic stuff, but still worth the time:

    http://access.jibc.bc.ca/avalancheFi...onse/index.htm

  24. #49
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    Feb 2008
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    There is kind of a magic space in the middle 30-45 degree range (with 38 being the most likely to slide). Anything less than 30 is not very likely to slide, and anything above 50 is lessening the likelihood of a slide, with over 55 degrees also very unlikely to slide
    I gots the jacket with the blue fox fur

  25. #50
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    Oct 2007
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    Quote Originally Posted by Shredgar View Post
    Another great thread from LeeLau.

    Carry a clinometer & know the slope angles.

    Choose the low risk line for the ascent.

    Windward exposures will not have as much loading re: new snow, but will be thinner snowpack re: faceting. It is a trade off.

    Approach suspect terrain from above w/cornii drops & ski cuts.

    While descending, ski cut convex microterrain features & pause to watch for any results.

    Beware terrain traps, look for the ridges, not the gullies, nibble the edges, avoid the bold centerpunch line if not certain (that one has saved me).

    One at a time, safe place to safe place & CLEAR THE RUNOUT.
    I especially agree with the idea of carrying a clinometer. In my experience, estimating slope angle can be very difficult.

    Quote Originally Posted by jon turner View Post
    Seems pretty thorough here. I think it's worthy to note again that just because a slope has trees doesn't mean it's anchored. As LeeLau said, if you can ski through the trees fast, they probably aren't tight enough to anchor the slope.

    I'm not an expert on digging pits, but this is something I picked up from my avi class, maybe others could chime in on their opinions of this:

    One thing I thought was interesting from my Avy 1 class is that a pit should be used to decide not to ski something rather than to decide to go forward with skiing a slope you are nervous about.

    By that I mean (4 scenarios with digging a pit):

    1. If you're sketched out by a slope, getting a good result from a shear test shouldn't make you change your mind and think the slope is safer. (I think this one isn't always obvious to people)

    2. If you think the slope is pretty safe, and the shear test is bad, it might make you change your mind and think the slope is less safe.

    3. If you think the slope is safe and the shear test is good, it's possible you are good to go with skiing the slope.

    4. If you are sketched out by a slope and the shear test is bad, it should be obvious that you shouldn't ski the slope (almost left this one out because it seems common sense)

    I think my instructor's main point here was to use your observations and smart travel decisions first, then add the pit as a last piece of the puzzle. If you are already skeptical about stability, it's probably best to turn around than use a pit to make yourself feel safer about the slope. Pits are more useful if you dig one in a similar place over a period of time such as in the same area at a similar aspect every week or two and you look at the progression of the snowpack as new snow piles up. You also want to pick the slope/aspect you are likely to ski. Digging a pit on a slope/aspect taht is not representative of what you are skiing is not really helpful. The instructors mentioned some studies that were done making snowpits all over the same slope and getting pretty variable results from the pits.
    So what's a good pit result and what's a bad result? I'd like to know how other people use pits to make decisions. Obviously an easy shear test could be indicative of a problem, while a very hard or non-existent shear would be more stable. But it seems like a big gray range in the middle.

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