Avalanche Discussion

It's not just what you do; it's how you do it. There was a night-and-day difference between how Jason and I "skied" that slope. From personal experience with wet slides I'm effectively 100% sure that I would have been carried in a similar avalanche, had I treated that slope the way Jason did. I'm not sure why you insist that this is related to unpredictable triggering.

You're discussing an experience I witnessed firsthand and I think you're making an unwarranted and inaccurate conclusion. I'm not sure what the utility of that is. I don't think there was anything unpredictable about that particular slide.

My advice to anyone would be to always follow safe travel protocols; approach changes in the terrain, the aspect, and the slope angle with caution; and never trust second- or third-hand observations and conclusions. The situation on Fortress was easily preventable with these prescriptions.

Thank you Gary, I agree. My addition about trigger points relates to what you mentioned about the change in behavior of the snowpack with buried surface hoar in relation to trigger points. The Cement Basin avalanche had seven people on the slope and the last person triggered the avalanche on buried surface on a 25 degree slope leading into a 38 degree convexity.

Skykilo references this point, he skied the same area then Hummel followed with different results and consequences. Rudi had a lot of people out on the slope yet it was triggered on a 10 degree slope near the top of the ridge, where the snowpack was shallow enough for Kelly to impact the weak layer.

One of the surprise factors of avalanches class 2 and larger is the size, often catching people on lower angle terrain and propagating much wider than anticipated. I believe knowing the layer exists and results have occurred on it, should be a red flag to not test this when there are possible consequences.

I believe your words "not to test this when there are high consequences" don't mean that one shouldn't test or observe the snow but rather with high consequences one shouldn't bet one's life on the test results - am I right?

We should always observe the snowpack and make appropriate tests - if nothing more than to learn something for future use. But it is a lot different making a snowpack test for academic reasons than it is to make a snowpack test and then to bet your life on the results. When the consequences are high, I think it wiser to play it conservatively. With sufficiently deeply buried weak layers - Persistent Weak Layers -  this is especially true. But that doesn't mean that observing the snowpack in a variety of ways isn't best practice. Otherwise one sets one's self up for the situation where one's perception of stability is for good stability when there may actually be isolated locations of instability.

I remember heli skiing once in the north cascades back around 1978. Good new snow and stability semed to be the rule. Then we came upon one particular slope and avalanche path that was 18" of new snow overlying classic depth hoar. Apparently this particular slope had avalanched to the ground early in the winter and then the shallow depth of the snowpack allowed for depth hoar formation. Although this is an unusual situation and in my experience west of the crest, in mid to late winter, unique, it still happened. At that point in my Cascade snowpack career I knew very little about the behavior of depth hoar - although I recognized it as such. Luckily it didn't slide as it was a big slope. In retrospect ( and maybe even at the time as I faintly recall) I believe the reason it didn't avalanche was probably that the overlying new snow wasn't sufficiently cohesive in that particular instance.

When other people ski a slope with these buried weak layers, that can create a negative feedback loop, if other people skied it then it is okay. This is true of early season snowbridges over crevasses as well.

I think that is true even in snowpacks absent persistent weaknesses. There seem to be two good points there: 1) In higher risk avalanche terrain and conditions avalanches can happen, and 2) Just because someone else has skied a slope doesn't mean it it safe.

Sky brings up another good point, that the precise line - micro routefinding - one takes can make a difference. I would just argue that with weak layers like facets and surface hoar in particular, knowing where that line is may be beyond human capability for most of us. 

"My advice to anyone would be to always follow safe travel protocols; approach changes in the terrain, the aspect, and the slope angle with caution; and never trust second- or third-hand observations and conclusions. "

I could not agree more with Sky, he nailed it precisely. I would emphasis the part about never trusting second-or third-hand observations and conclusions--including this thread. Buried layers?, Ice glazing? In the Cascades! You have got to be kidding. Maybe as a short term issue but very rarely is it a concern over the course of the winter. Our dramatic temperature swings take care of that

I doubt the hundreds of people that were just killing the Baker backcountry yesterday followed this thread. They talked to the ski patrol, "great right side up snowfall with super bonding to the crust" and sniffed out the snowpack for themselves.

I skied 15 days in the Selkirks the winter of the accidents and had a great time. If we listened to half the experts sitting on their computer making conjectures we would have stayed home. One day Troy Jungen and I and others were heading out and got stopped by a CBC film crew. The next day's story was, "Skiers risk death in killer backcountry". No, we told them that sticking to good terrain was the key to a successful and safe trip.

I have the very high respect for the experts on this website who share their knowledge, it just think in this case they are making judgements about the snowpack that don't fit the reality for those of us putting skiis/snowboards to snow.

Here is my advice for anyone wanting to learn about staying safe in the backcountry: Before you spend money on a course, read all the reports and spend time digging pits, just beg someone who has been staying alive for 30 plus years to take you out and teach you how to read terrain and routefind. Perhaps that is simplistic, but it has worked for me. That should be the most important part about avalance safety.

In reality persistent weak layers in the Cascades tend not to be as bad or as persistent as in areas farther away from the coast. Still, weak layers here often last for 3 weeks or so (with respect to skier triggering) after snowfall begins - serious snowfall, not the dribble we've seen of late. However, Cascade persistent weak layers seldom disappear completely and usually resurface with heavy loading in the winter or melt cycles in the spring - although these are typically not the situation for skier release. But rules of thumb like,

"Buried layers?, Ice glazing? In the Cascades! You have got to be kidding. Maybe as a short term issue but very rarely is it a concern over the course of the winter. Our dramatic temperature swings take care of that."

are made to be broken. Recall the fatal 15' slab avalanche at the Baker ski area that was most likely (M. Moore) skier! released in February of 1999 or the natural 15-25' slabs of early February 1990.

Along the Cascade east slopes persistent weak layers seem to be the norm all winter long from my experience and the only thing that mitigates avalanche cycles there is the lack of sufficient load - few storms reach the east slopes with heavy enough snowfall to make the weak layers critical - although one certainly did near Washington Pass this January.

Over a long enough period of time - and who knows what that is - the Cascades will have winters like the Rockies and the Rockies will have winters more typical of the Cascades. Almost all of my close calls have been with persistent weak layers - and in the Cascades - since the very early days of my skiing career.

Obviously terrain is the key but a lot of smart and very experienced skiers have been caught while applying a new snow regime mindset to a snowpack with unusual characteristics. Safe terrain parameters shift when conditions shift.

Triggered 12-15" slab on 35-40 degree north aspect yesterday near Mt. Baker at 4500'. Propagated 50-60 feet wide and slid on a rough crust with some faceted grains on top of the crust. Do not know if there was any surface hoar involved but it is possible given the location. The recent snow in this location was not cohesive at all so the slab itself was an older and seemingly settled and faceted layer from earlier snows. I noticed the underlying snow in this location immediately before the slab released was harder than in other locations I'd skied and traveled on. I checked at a noticeable convexity and expected a sluff but instead a slab broke at my control line. I don't know any reason the snow should have been harder underneath in this location - as far as I could tell this was a random isolated slab in a situation where 3"-10" sluffs were the norm on steeper slopes. I would note that between 4000' and 5500' the recent snow from Monday was loose, not cohesive, but that underlying this 6-14" of recent snow the older surface was much more variable with wind slabs, settled snow, and warming crusts in evidence, all now somewhat faceted on shady aspects. A harder crust (the bed surface of the slab) generally underlies this structure. Despite the slab I would rate the hazard Moderate (although down to 4000' near Mt. Baker). Still this can't be the only lingering slab.

It clearly was an example of the behavior of persistent weak layers.

I was not at risk in this situation but was surprised by the slab. The lack of cohesiveness with a slab points to a very bad bond in this location. This snowpack would not support much load. Fortunately or unfortunately (depending on one's viewpoint) heavy loads of new snow aren't likely to be in our future any time soon.

It is interesting to note that Canadian forecasts also speak of isolated slabs. As a matter of fact there is good reason to believe that underlying surfaces throughout the west are likely to have a variety of facets, surface hoar, and degenerating crusts because of the long lasting and unusual weather recentlly across the entire area south of northern Canada and west of the Great Plains.

Gary - If it isn't a secret stash, can you post a map or description of where you were. Headed out this weekend and want to know if this is in the same general vicinity.

Thanks