Relative safety of skiing in the trees

My feelings about trees and avi danger is that they would tend to decrease the likelihood of significant propagation by breaking up slabs at every tree (trigger point). Of course this does nothing to mitigate the danger from above as has been pointed out. I do worry about the increased potential for buried surface hoar in the shelter of the trees, though. A small release in the wrong sheltered area could be just as deadly as the largest exposed release.

I've watched a slab release in skiable-but-dense trees. It was on a rollover, and fortunately was only about 8" deep and didn't travel far downslope as it came to a stop on a bit of a bench, and the skier who triggered it remained above it, and the other two of us a bit below and off to the side. It had no problem propagating through and around the trees.

But yes, my observation has been that in storms, the new snow deposits are not as deep in the dense trees as out in the open, as some comes to rest up on the canopy. It often seems to have a different consistency too - seeming not quite as likely to propagate cracks as the snow in the open. And I've always imagined that when the sliding surface would be the last crust layer, the highly textured tree-bombed surface in the forest would provide at least some traction (dunno how valid a thought this is though, and in the case noted above, the slide either started on or travelled down to the last crust layer...). But of course sometimes the sliding surface is in the new snow, and sometimes the new snow in the forest, as on the day noted above, is quite reactive.

Perhaps "no protection" is overstating the point slightly, but I'm quite sure that "no guarantee" is spot on.

Great data in this thread.

* According to The Avalanche Handbook, "avalanches in trees are infrequent but they do occur". Published research finds that backcountry skiers in North America are much more likely to die from traumatic injuries. Trees are definitely a factor in these findings. Do what you will with this information; it mostly says "it depends".

* Extremely unstable storm snow is what you can expect to lead to avalanche formation in trees. This would include instabilities that form because of temperature changes during storms.

* Limitations to line-of-sight and the presence of obstacles on the slope are factors that can make rescue extremely difficult.

* DG writes: If there truly was no relative safety in skiing in trees, then all other things being equal (slope, snowpack, elevation, etc.), then it seems like you'd always be safer to ski on a completely open slope, because at least then you wouldn't have the hazard of being strained through the trees if a slide did occur.

( Yes, this can be correct. As Joedabaker says, experience teaches you which slopes are better on which days. )

* Joedabaker writes: For the most part you are in a better position in the treed areas vs the open slopes. You need to evaluate that on your own. I have safe skied slab snow in the trees too. When you gain more experience with the snow conditions it is possible to find a safe place to ski in nearly all alert levels.

( Exactly right. Experience is the key. )

* Marcus writes: So yeah, it all depends on the conditions, but if it's steep enough to slide, it might, whether there are trees or not.

( Exactly right. )

* Jim Oker writes: I've watched a slab release in skiable-but-dense trees.

( Yes, I've seen this happen before as well. I reached the same conclusions about propagation as you did. )

* Jim Oker writes: ...the highly textured tree-bombed surface in the forest would provide at least some traction...

( Exactly right. Rough, warm, soft is better for bonding than Smooth, cold, and hard. )

Thanks for all my feedback on my question. It's great how much collective experience there is in this forum!

wasn't that avy that killed the guide and broke the femur of her partner in Montana ( last year)? in the trees?

Also wanted to add.

Often times, people think "well, the snow is unstable, and we'll be safer in the trees". As Joedabaker et al. point out in this thread, the choice to ski trees is based on a variety of factors that experienced folks can sort out. Less experienced folks may not yet possess the tools to make these judgments. Serious errors may arise.

So if you're not sure, for whatever reason, then the following applies: When the snow is highly unstable, you have to manage exposure by limiting slope angle. It is always safe to limit exposure in this fashion, and sometimes it will confine you to very low angle terrain.

Later, as you build experience and skill, you'll learn how to determine whether or not the trees are a better choice.