Feb 8, 2014, Lane Peak/Fly Couloir, Slab Avy
2/8/14
3151
3
Morning/approach
A group of us went down to the Tatoosh on sat and got to Narada falls parking lot around 9:45. We had been touring around pinnacle the week before. We had found very good stability, absolutely no signs of avy or even sluffing. Our first observations this week were that there had been some high winds as the first hill out of parking lot had been completely scoured from the week before. There was a fresh, very light, layer of about 5" of fresh which matched telemetry data for the area. Several of us have been wanting to ski the zipper and the fly so we had been planning to make a decision at the parking lot. The night before I had looked over NWAC and the forecast for 'near treeline' (which is what I would consider the couloir, pls comment if you disagree?) was moderate. I was figuring that all the storm slabs had stabilized since the last storm 9 days ago and that wind slabs were the primary concern. From the parking lot two of us made the decision to at least skin the apron below the zipper and assess. We skied down to the lake / opening and skinned to 70 ft below the Zipper. We booted up to the base of the zipper and it was clear the coverage was low and the couloir was not all that appetizing so we headed over to the fly.
The Fly / Slab Avalanche
As we approached the fly opening I had noticed a small crown near the lookers left of the entrance. I had taken this to be a small slab from the storm a week ago. As it turns out, this was actually a slab set off two days ago by another ski group (see TR from FEB 7th) I would guess wind and snow had reduced the size / appearance. At the base of the couloir we dug a pit. No failure with wrist, a slight crumple after several elbow hits, and no additional failure with full arm hits. The column never shear failed, only a slight compression a perhaps 1/4" shift. There were no hard or really even crusty layers at this point. We were able to get three gloved fingers in at each layer. We took this as a very positive sign that stability was good, again my main concern from reading NWAC and previous weeks experience was were any wind slabs we would find at the top. We started booting up. It was very slow going, sometime we were digging through waist deep snow. Snowpack was fairly variable on the way up. There were several sections where a firm layer would show up that you could hold your weight. I was not concerned with the variation b/c the top layer was only 6" deep. Then you would be back to waist deep snow. I cant believe another group had been up there a day earlier, we did not see any signs of a boot or ski track. Near the top, the couloir gets fairly steep, perhaps approaching 45 deg, then hangs lookers right. We had started talking about digging a second pit. I cut two mini blocks down to the first consolidated layer (not really a crust but clearly a more dense layer), which at this point was approaching 12-14" deep. I did a quick test and found consolidation between the top and consolidated layer to be very strong. No shear was observed on my mini-test. Considering we were still booting and not skiing I felt we were safe to continue up the steep section and get to the last section of the couloir where we could transition and dig another pit. At the steepest section I asked my ski partner if I should take lead and was just about to reach him when I started feeling myself floating back down the couloir. I was sliding backward on a 40-45 deg slope and could see the snow breaking up around me. I had about a second thinking 'fuck, im in a slide, hope its shallow, worst case will be a long ride into the couloir wall'. I immediately started arresting with my ice axe. Im glad I had it with me, I think alot of people hike it w/ just two poles. I stopped about 30 feet down, and looked over my sholder to see the slab continue down the rest of the couloir. It only took the top 6-10" top layer with it so it was not a deep avalanche. We hiked down a good portion of the couloir and then transitioned to ski out the last half.
Conclusions
-First, I was fortunate that the slab released when I was close to my ski partner while booting. If I had been much farther behind my partner, it may not have been possible for me to arrest.
-While the layers were showing cohesion and stability, extreme caution needs to be taken when the slope angle gets steep.
Pictures
http://www.flickr.com/photos/18200822@N04/sets/72157640703738405/
A group of us went down to the Tatoosh on sat and got to Narada falls parking lot around 9:45. We had been touring around pinnacle the week before. We had found very good stability, absolutely no signs of avy or even sluffing. Our first observations this week were that there had been some high winds as the first hill out of parking lot had been completely scoured from the week before. There was a fresh, very light, layer of about 5" of fresh which matched telemetry data for the area. Several of us have been wanting to ski the zipper and the fly so we had been planning to make a decision at the parking lot. The night before I had looked over NWAC and the forecast for 'near treeline' (which is what I would consider the couloir, pls comment if you disagree?) was moderate. I was figuring that all the storm slabs had stabilized since the last storm 9 days ago and that wind slabs were the primary concern. From the parking lot two of us made the decision to at least skin the apron below the zipper and assess. We skied down to the lake / opening and skinned to 70 ft below the Zipper. We booted up to the base of the zipper and it was clear the coverage was low and the couloir was not all that appetizing so we headed over to the fly.
The Fly / Slab Avalanche
As we approached the fly opening I had noticed a small crown near the lookers left of the entrance. I had taken this to be a small slab from the storm a week ago. As it turns out, this was actually a slab set off two days ago by another ski group (see TR from FEB 7th) I would guess wind and snow had reduced the size / appearance. At the base of the couloir we dug a pit. No failure with wrist, a slight crumple after several elbow hits, and no additional failure with full arm hits. The column never shear failed, only a slight compression a perhaps 1/4" shift. There were no hard or really even crusty layers at this point. We were able to get three gloved fingers in at each layer. We took this as a very positive sign that stability was good, again my main concern from reading NWAC and previous weeks experience was were any wind slabs we would find at the top. We started booting up. It was very slow going, sometime we were digging through waist deep snow. Snowpack was fairly variable on the way up. There were several sections where a firm layer would show up that you could hold your weight. I was not concerned with the variation b/c the top layer was only 6" deep. Then you would be back to waist deep snow. I cant believe another group had been up there a day earlier, we did not see any signs of a boot or ski track. Near the top, the couloir gets fairly steep, perhaps approaching 45 deg, then hangs lookers right. We had started talking about digging a second pit. I cut two mini blocks down to the first consolidated layer (not really a crust but clearly a more dense layer), which at this point was approaching 12-14" deep. I did a quick test and found consolidation between the top and consolidated layer to be very strong. No shear was observed on my mini-test. Considering we were still booting and not skiing I felt we were safe to continue up the steep section and get to the last section of the couloir where we could transition and dig another pit. At the steepest section I asked my ski partner if I should take lead and was just about to reach him when I started feeling myself floating back down the couloir. I was sliding backward on a 40-45 deg slope and could see the snow breaking up around me. I had about a second thinking 'fuck, im in a slide, hope its shallow, worst case will be a long ride into the couloir wall'. I immediately started arresting with my ice axe. Im glad I had it with me, I think alot of people hike it w/ just two poles. I stopped about 30 feet down, and looked over my sholder to see the slab continue down the rest of the couloir. It only took the top 6-10" top layer with it so it was not a deep avalanche. We hiked down a good portion of the couloir and then transitioned to ski out the last half.
Conclusions
-First, I was fortunate that the slab released when I was close to my ski partner while booting. If I had been much farther behind my partner, it may not have been possible for me to arrest.
-While the layers were showing cohesion and stability, extreme caution needs to be taken when the slope angle gets steep.
Pictures
http://www.flickr.com/photos/18200822@N04/sets/72157640703738405/
Dang! Glad you made it out, and props on the self arrest!
author=EvryDayzSatday link=topic=30690.msg128381#msg128381 date=1391994725]
The night before I had looked over NWAC and the forecast for 'near treeline' (which is what I would consider the couloir, pls comment if you disagree?) was moderate.
I think that is such a great question with the new format to the forecast. I have been trying to interpret it from the perspective of wind exposure and anchoring potential and not as much altitude (temp, snowfall amount, cohesiveness, etc, at high elev) . What do others think?
I can't answer your question because I can not keep the two incidents from there this weekend out of my thought process. Had you asked that question on Friday I may have felt certain that the Fly was "near treeline".
Thanks for the write up and glad there were no bad consequences.
John
Glad you're okay, thanks for the TR. Two thoughts:
The NWAC forecast is a broad, general tool - it's not meant to be applied to slope-scale decisions (e.g. the Fly is near treeline = moderate).
Pits are great indicators of what's going on in that immediate vicinity (i.e., within 4-5 feet), but are kind of like the opposite of the NWAC forecast - they're not very good predictors of stability even 10 feet away when the terrain is complex. For myself, I try to use pits to confirm my fears, not my dreams, if that makes sense. I.e. a pit shouldn't give me the green light, but it can damn sure give me a red light.
Not saying I practice all that consistently, but I think it's good stuff to keep in mind. Glad you had your ice axe out!
The NWAC forecast is a broad, general tool - it's not meant to be applied to slope-scale decisions (e.g. the Fly is near treeline = moderate).
Pits are great indicators of what's going on in that immediate vicinity (i.e., within 4-5 feet), but are kind of like the opposite of the NWAC forecast - they're not very good predictors of stability even 10 feet away when the terrain is complex. For myself, I try to use pits to confirm my fears, not my dreams, if that makes sense. I.e. a pit shouldn't give me the green light, but it can damn sure give me a red light.
Not saying I practice all that consistently, but I think it's good stuff to keep in mind. Glad you had your ice axe out!
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