Hey all. I'm interested in learning about how you all go about choosing a location for snow pits. Specifically, what are some best practices in assessing a slope when coming over a ridge line? For example, you climb the west face and plan to drop in on the east. Lets assume there is no cornice to cut.
Do most people set an anchor and belay down a few yards and dig a pit while on rope? Do many of you carry rope with you?
How do you assess a slope when you come over a ridge and haven't had any test slopes or any similar aspects to investigate?
Joined: Wed Oct 31, 2012 7:42 am Posts: 34 Location: Bozeman
Even if you belay down and dig a pit it will be unrepresentative of the slope you will ride. Climbing a west slope and dropping in on an east facing slope with prevailing westerly winds will typically result in a deeper snow pack near the ridge than lower in the slope due to wind deposition. This will on the long term provide more stable snow, but in the short term during or shortly after a wind event less stable snow than the rest lower on the slope.
That is why I'm curious what people do. Everything I've read indicates that the upper part of the slope, close to the ridge, will be have larger deposits of wind transported snow. So digging right at the top won't tell you anything about mid-slope. What do you do in this situation websherpa?
I think before you even step on snow you should have a basic understanding of what the snow is doing from the UAC. Once you have a basic idea of what the issues are you can start planning your tour. Is it going to be trees, meadows, peaks, etc. I'm looking at general snowpack, deep slab, wind slab, new snow, crust sandwiches, etc. New snow if any, how much and what density. Winds especially, danger rose readings, direction, speed. Recent activity, observations from the UAC and here.
Once on snow I'm trying to use my own observations with what I read to form my final decision. Depending on what your looking for I like punching my handle around to get a feel for layers/crusts, density inversions,etc. Little hasty's for wind slab, or to check how new is bonding to old. Pit's to see how a persistent weak layer heals over time or with the weight of new snow and for general snow structure. I'm also looking for recent acitivity and taking advantage to jump around on every little small test slope I come across on the way up.
Known: winds hammered higher elevations, possible wind slab. Recent activity on the same aspect.
Obvious wind slab, clean shears with the hasty. Jumped on some test slopes stubborn.
Obvious cross loading.
Pocket, slight convex/roll feature, rocky area. Changed my exit plans which were a gully exit and took the long way back out.
More to the point of strategies once on top. If theres a cornice I'll kick it but I think more importantly I think is to have a descent plan. I think you can ride many slopes that have a potential to slide (not including deep slabs of course just wind slabs, soft slabs, etc.) by choosing a smart route. Intentionally avoiding sweet spots, ski cutting, considering your runnouts, and having a general plan, cut here straight there.
I watched Alta bombs pulliing out similar soft slab pockets. I kicked some cornices with no result. My plan was couple turns and then straight it, thinking I might find a pocket in the apron. I did, and was able to use it for the up.
This one speaks directly to what you asked. This is this year, no new snow but winds were in the 70mph range. Slope were getting wind loaded. It was a blessing in a sense because it reset lines that were probably already ridden. You climb W and ride E/NE, so I had no first hand data what conditions were like. When I got to the top the winds were nuking and the slope was obviously cross loaded. However it was isolated and I felt I had a good plan for the descent. Ski cut to perfect safe zone. Stay riders left on a more bench lower angle part of the slope then cut into the chute and straighten out the nose. I chose not to ride a fun line lookers right in the photo because it had a small roll and a sharp turn in the runnout and instead take my same line down for lap two.
Those are my thoughts. Long winded but It's fun to organize my ideas into writing once and a while, thanks for the great post.
My point as it relates to the original question is kind of spread out in all my tangents and is confusing so I thought I would summarize what I was trying to say. I think the idea is the same whether it's a slope you have hands on data for or a slope you have no hands on data for. That is what do you do with the information you already have or observed so far, what is your final decision. Hopefully, you already have some information, wind speeds, wind direction, new snow amounts, etc. You have a general plan based on the current hazards. If it's deep slabs and persistent weak layers your simply writing certain slopes/aspects/angels etc., out of your plans for the day and sticking to meadows or S. faces etc. If it's wind slabs or small soft slabs that are not really propogating but pockety etc., your looking to avoid those obvious features that hold pockets and really making a plan for the descent, ski cutting if possible, paying attention to runouts, rolls and other features, etc. so if you do find a pocket you can react. I hope that makes sense. I think roping up and digging a pit is excellent, really just roping up and doing a hard ski cut across the sweet spot would even be better. But like you said spacial variability, slight changes in aspects, features like gullies and roll overs, etc all play a role.
Edit to add one more thing related to my pictures. In the first instance I had multiple red flags plenty of hands on information yet I justified riding the slope which was a bad decision. In the second and third instances I no chance to dig a pit yet felt comfortable with the info I had observed and read and my overall plan, the terrain, etc enough to justify the decision which I feel were good choices.
Utah - I must of read this post like 5 times through over the past few months. I'm sure it won't be the last time either. Thank you so much for the lengthy response. It's super helpful to have the pictures with overlaid commentary. I usually keep it pretty mellow but as I learn more I'm looking to get into some more fun and steep terrain.
Utah - I'm curious about the run with the soft slab. Did you suspect a pocket in the apron solely by your observation of Alta ski patrol during the ascent or were their other clues as well? Why on the apron and not in the chute as well?
Alta gave me a bit of info on aspect and elevation and the apron provided a nice prone to avy feature. The chutes and rock features in the cirque are steep 40+ so snow doesn't really stick it flushes itself as snow builds and gravity wins and ends up in the apron which is a 35+ degree wide open bowl perfect for avalanching. Your question prompted me to pull out my "Chuting Gallery" book which talks about an avalanche that happened in that same chute. The picture of that slide is identical to the slide I triggered a bit deeper though. So I knew it could slide which is also why I bombed that stuff, I was afraid of what I would find in the apron. Take care.