Tahoe Slides 1/14/2016, Coldstream(JT Holmes) and Tallac Corkscrew

[SchralphMacchio]

This thread is to discuss either of the Tahoe-area skier-triggered avalanches on 1/14/2016. In both incidents, a single skier/snowboarder was caught, carried, buried (partially or completely), and successfully recovered via companion rescue.


Incident at Coldstream with ski industry professionals, one skier (JT Holmes) was caught, carried, buried, and successfully recovered via companion rescue
Sierra Avalanche Center Incident Report: Not Available
Location: Coldstream area, east of Sugar Bowl ski area, ~7500' elevation
Media Links:
-Daron Rahlves TGR Interview: http://www.tetongravity.com/story/ne...m-an-avalanche
-Reno Gazette Journal Article: http://www.tetongravity.com/story/ne...alanche-burial
-TGR Media Post: http://www.tetongravity.com/story/ne...alanche-burial


Incident on Mt. Tallac with recreational party, one snowboarder caught carried and partially buried, recovered via companion rescue
Sierra Avalanche Center Incident Report: http://www.sierraavalanchecenter.org...corkscrew-bowl
Location: Mt. Tallac, Corskscrew Bowl, ~9000' elevation


Sierra Avalanche Center Advisory for 1/14/2016
http://www.sierraavalanchecenter.org...14-070243#null

On slopes steeper than 32 degrees, CONSIDERABLE avalanche danger still persists on NW-N-NE-E-SE aspects in near and above treeline terrain due to a combination of wind slabs and persistent slabs. Even though the window for natural avalanches may have passed, human triggered avalanches remain likely. Unusual avalanche conditions exist. Avalanches on steeper slopes could be remotely triggered by a person standing in lower angle terrain. Careful snowpack evaluation, cautious route finding and conservative decision making are essential.

I decided to co-mingle incidents into a single discussion thread, because even though these were totally separate groups with separate decision making dynamics, both accidents occurred on the same day in terrain along the Sierra Crest near the West Shore of Lake Tahoe: the avalanche advisory, avalanche problem setup and snowpack / weather history apply fairly closely to both of these areas. However, the Coldstream incident and Mt. Tallac incident did occur at significantly different elevations (7500' vs. 9000'). In both incidents, the first skier did not trigger the avalanche (it was actually one of the last skiers in each group).

[SchralphMacchio]

Quoting lepistoir from the Tahoe Thread:

Just heard Darren talking about JT's incident on TGR's podcast.

https://m.soundcloud.com/tetongravit...#c=1088&t=0:01

Hearing the details, I'm impressed with how stupid lucky he got.

He was second to last in a group of 8 plus guides and went a little further left than everyone else. Buried head first, face down, six feet deep for six and a half minutes. There were no visual clues for the search and the lowest beacon reading was 2 meters. He also got swept over a cliff. There were at least 8 skiers and guides on hand for the shoveling and extraction. JT was unconscious when they reached his head, with snow packed in his mouth, barely breathing. There were 3 EMTs in the group and a snowcat to help with the return, but he recovered consciousness and was somehow uninjured so was able to get out under his own power. I think it's worth listening to the podcast understand more about running a quality rescue, and about how pushing the boat out a little further can have horrible consequences.

[AKbruin]

I agree with your comments elsewhere about group dynamics, false security, and the importance in line choice. In think that was in connection with the Yellowstone Club avalanche, where I think the group agreed to ski a safe slope and an experienced patroller made (perhaps an impulsive) decision to ski a riskier line that ended tragically. I'm pretty sympathetic to this kind of error. I could see myself having a temporary lapse in judgment. Something to keep in mind.

Incidentally, I skied an well-treed east-facing aspect around 8800' in the Rose area early the morning of the Corkscrew and Coldstream avalanches. It was probably around 30 degrees. My partner and I were aware of the windslab issue and chose terrain that wasn't particularly steep or overly exposed to wind loading. I didn't dig a formal pit, but I tested different slopes on the climb up and it felt pretty stable where we were. I'm not offering this in support of any conclusion but just as another data point.

[lepistoir]

One thing that really surprised me about this incident is that it doesn't seem JT was wearing an airbag or an avalung or I haven't heard any word about either being used. Does anyone else know more than me?

[adrenalated]

Curious after reading the Corkscrew accident account.

It seems like the snowpack conditions are unusual for the Tahoe area, and perhaps more reminiscent of a continental snowpack than usual with PWLs?

If so, it seems like the familiarity heuristic trap was a HUGE player - the group traveled to an area that is typically considered safe, but failed to recognize that snowpack conditions were atypical for the area. Or perhaps did recognize it but did not adequately account for it in the decision making.

We have a similar situation in CO right now. Some of our usual facet layers are unusually well developed on some aspects, and there have been a few decently sized slides on slopes that are not usually particularly dangerous, including a fatal accident near Crested Butte yesterday.

Persistent slabs are tricky beasts. Stay safe, Tahoe folk.

[mcski]

And where is the GO PRO footage?!?! Should have multiple angle viewing with that crew.

[SchralphMacchio]

doesn't seem JT was wearing an airbag or an avalung

I don't have any info other than Daron's interview, but given the level of detail from his interview it seems that if JT had an airbag that would have been discussed.

It's pretty clear that the Coldstream incident was a guided party, so BGnight's criticism on the TGR Facebook page was somewhat misdirected. Having been victim to this myself, even as a trained individual it's very easy to fall under Expert Halo and put a lot of faith in other people when you are being shown around in "their" terrain.

The decision making is interesting to review, because given the recent natural activity in the area that was reported in the SAC bulletin and also clearly visible from the party's vantage points, there were immediate red flags regarding reactivity of the avalanche problem in this zone. I wonder if heuristics and familiarity with typical Tahoe avalanche problems were a factor, and how review / identification of the problem played out. There were two pits dug by guides, but in my experience pit data are not usually shared with clients, just a summary of the guide's interpretation of stability. I'd love to know if localized / spatial variability was a factor at all.

Operationally it sounds like this was a very well managed group; only one person exposed at any time and the safe zone was not compromised (e.g., not poorly selected, unlike what we often see in other multiple-persons-caught incident reports). The recovery time of 6:30 minutes for a 6' burial is astonishing and mindblowing; with heavy wind-loaded sierra cement and such a deep burial this team had to have been using very efficient digging techniques to move that much snow. I've heard of large rescue groups not being well directed during shoveling, leading to less efficient recovery times.

I really hope that PCS eventually submits more information to SAC or The Avalanche Review because the operational takeaways from this accident will be really valuable, even if not discussing the decision making framework and perceived margin of safety immediately prior to the incident.

Incidentally, I skied an well-treed east-facing aspect around 8800' in the Rose area early the morning of the Corkscrew and Coldstream avalanches. It was probably around 30 degrees. My partner and I were aware of the windslab issue and chose terrain that wasn't particularly steep or overly exposed to wind loading. I didn't dig a formal pit, but I tested different slopes on the climb up and it felt pretty stable where we were.

I'll ask you this:
a) were you concerned at all, and or thinking at all, about the persistent slab / surface hoar layer or were you more focused on recent windloading / windslab?
b) what was your level of confidence that a persistent slab problem did or did not exist in your selected terrain, and
c) if you acknowledged the probability of that problem existing in your terrain, what do you think made your willingness to fuck with it?

[SchralphMacchio]

Corkscrew accident account ... It seems like the snowpack conditions are unusual for the Tahoe area, and perhaps more reminiscent of a continental snowpack than usual with PWLs?

If so, it seems like the familiarity heuristic trap was a HUGE player - the group traveled to an area that is typically considered safe, but failed to recognize that snowpack conditions were atypical for the area. Or perhaps did recognize it but did not adequately account for it in the decision making.

Yes, not usual for California. Typical SH cycles are followed by some combination of sun/warm temps, strong winds, and/or wet snow at the start of the storm with deep accumulations typical (generally > 1" of SWE in an event, and 4-6" of SWE in 48 hours can happen multiple times per season). This tends to destroy SH layers before or during precip events. In recent years most of our persistent slab problems have been coming from NCF formation rather than SH.

I'd suggest that our snowpack is a bit more like Interior BC right now, with a very deep pack but recent near surface weaknesses that have been buried by slow accumulations of gently-layering snow rather than typical rapid loading. I haven't been touring long enough to say "the last time" we had a snowpack development cycle quite like this one.

I will say that generally warm temps and stable snowpack have created outdated and "less than ideal" practices within the Tahoe BC community, where heuristics and rules of thumb generally dictate decision making.

My very personal and very limited assessment is that people in the community have a tendency to "ski the trees" when it storms and wait 48 hours after a dump before getting on bigger and more committing terrain. Problem characterization and problem based management of terrain does not feel widespread to me among people I talk to who get after it. As a result a lot of people here are generally good at managing near surface instabilities such as storm slabs and windslabs, but the higher profile (fatal) accidents in recent years have tended to happen during more uncommon persistent slab formation.

[TahoeJ]

Seems like very poor decision making (there's just no getting around that), very good rescue technique. The dig out time, with this snow, is certainly impressive no matter how many people you have helping.

[snapt]

I think Happy treats that terrain a bit too much like its in bounds if he's had a lot of skiers on it in the season. When I inquired if stuff goes on a frequent basis I was told they get enough skier compaction to minimize it. His North facing stuff is steep and can be consequential with chutes, cliffs, rocks and trees. It's excellent ski terrain though, great fun.

My story is pretty similar to JT, a day where myself and touring partner wouldn't have touched that stuff, we got lulled into a false sense of security by the guides thinking it was good to go. It wasn't. From SAC's comments on FB it sounds like they're not supper forthcoming with info when incidents do happen. Bad for business I guess, but also bad for everyone else trying to learn from it.

[bodywhomper]

i know that complacency is not a heuristic trap described by mccammon, so i guess it falls under "familiarity"? but there have been many times where a SH or NSF have been identified by SAC, which then gets theoretically buried by the next storm cycle, gets reported in the advisory as a potential hazard, and does not become active as a PWL/S (there are a few exceptions). To me, i feel like it's a combo of hearing this issue before from SAC w/o experiencing any results (almost like crying wolf) and a lack of experience of the hazard in familiar terrain (both events). I would guess that for the guided group, there was likely a fair bit of trust placed onto the guides and with pros and filming, all the heuristic traps were stepped in.

in my mind, i'm thinking about the future of the season. Are we really heading into "Mod-X" territory? Is this thing going to stick around? will it quiet down in the near-term and crop back up (reactivate) after a few more storm cycles (or after a big thaw cycle)? or will it stay quiet for the remainder of the season? will it self clean in the cycle we're about to experience?

I find it interesting how SAC is now characterizing the hazard.

[AKbruin]

I'll ask you this:
a) were you concerned at all, and or thinking at all, about the persistent slab / surface hoar layer or were you more focused on recent windloading / windslab?
b) what was your level of confidence that a persistent slab problem did or did not exist in your selected terrain, and
c) if you acknowledged the probability of that problem existing in your terrain, what do you think made your willingness to fuck with it?

I knew of the potential hoar layer but didn't see much evidence of it in this particular area and was skiing terrain that felt generally safe for such slabs--e.g., not particularly steep, no real rollovers, and loads of trees. Nor did I see any natural avy activity. So, yeah, wind slabs were the primary concern, and it wasn't windy in the a.m. and the cornices were normal-sized. So I acknowledged the possibility of a problem--there's almost always a possibility--and concluded that it too small to avoid skiing altogether but large enough to exercise terrain management.

[SchralphMacchio]

there have been many times where a SH or NSF have been identified by SAC, which then gets theoretically buried by the next storm cycle, gets reported in the advisory as a potential hazard, and does not become active.

Oh yeah, disrespecting potential hazards is definitely human nature when they only bite you 1 out of XX times. I read in the avalanche review that if humans did not disregard dangerous outcomes with near-zero-probability we wouldn't really be able to effectively function. So, you know ... "I didn't realize the danger!"

The most compelling case study of this type of behavior, notable for its sheer collection of mass willful ignorance, is Saddle Peak February 2010 (Bridger Bowl):
http://www.mtavalanche.com/sites/def.../ISSW_2010.pdf

I knew of the potential hoar layer but didn't see much evidence of it in this particular area and was skiing terrain that felt generally safe for such slabs--e.g., not particularly steep, no real rollovers, and loads of trees. Nor did I see any natural avy activity. So, yeah, wind slabs were the primary concern, and it wasn't windy in the a.m. and the cornices were normal-sized. So I acknowledged the possibility of a problem--there's almost always a possibility--and concluded that it too small to avoid skiing altogether but large enough to exercise terrain management.

^That all sounds like a reasonable review of certainty vs. consequences. Your zone also has a different set of weather patterns from the West Shore.

[TahoeJ]

As of a few weeks ago my theme of the season has been: pretend you're in Colorado.

Not to divert this thread but here's a question: we can all agree this is not your normal Tahoe snowpack. Climate change related or just a coincidence?

Are we going to have to throw old Tahoe assumptions out the window moving forward? (Not to say they were ever 100% reliable)

[LightRanger]

I don't think snowpack problems are climate change-related per se. Increasingly extreme seasonal variability on snowfall accumulation, sure. There's literature out now about how the current/hopefully exiting drought was made worse by how crazy warm it was(not just dry) due to climate change. But snowpack problems on a given day or month isn't the same.

[SchralphMacchio]

I'd suggest that pinning a single season's worth of weather on a climate pattern that occurs over tens to hundreds of years isn't really sensible (season = datapoint, climate change = data trend over lots of datapoints). There is also a reason that there are things such as 10-year, 100-year and 1000-year avalanches - happening as a result of a unique sequence of seasonal weather events that may not necessarily be correlated with multi-year trends.

I'd also suggest that ski touring based on "Tahoe assumptions" is not exactly "doing it right." This same debate came up when the Tunnel Creek accident occurred in February 2012 ... a lot of locals and party members talked about how they weren't doing anything unusual or extraordinary for the conditions, but that didn't absolve the fact that the party was on a steep slope with persistent slab weaknesses identified in the avalanche bulletin. Avalanche training in the US has certainly updated how persistent slab problems are taught, but it's not like surface hoar isn't part of standard curriculum in Tahoe or the PNW.

Porter Fox asks in his book Deep if the snow and accident setup in Tunnel Creek was due to the changing climate. Honestly I think that's a cop-out for a failure in decision making, training, and group dynamics.

That said, the researchers and industry professionals Fox interviewed are concerned with shorter precipitation seasons as a result of climate change, and some data provides evidence of that. But I'm not sure there is any consistency in data and/or modeling regarding thinner snowpacks or colder snowpacks, which are things that make mid-winter snow more dangerous from a recreational perspective.

[TahoeJ]

Well, I don't tour based on "Tahoe assumptions" aka the Tahoe 24 (or 48) but a lot of people do. Or kind of do subconsciously to some degree. Anyway, while I agree such a limited amount of data (this season) would be absurd to draw any real conclusions, we're all obviously aware what a difference a few degrees can make, so I wonder if we're going to see a more volatile snowpack in the future, or at least a different set of trends.

Anyway, ugh, I apologize for even going the climate change route. Zzzz... let's just pretend I didn't.

[TahoeBC]

So my group was skiing the corkscrew on Tallac that day along with 3 to 4 other groups. We knew the avy forecast for the day, in fact the week before this zone was our target but after a brief discussion as it was a considerable day also we decide to hit a safer zone, which I kinda regretted later after seeing all the lines that did go down that day with out issue (Boy who cried wolf alluded to in a post above)

Some of the zones I've been skiing the week before have not had the weak layer that the SAC been warning about. Combine all the above with just the desire to ski lines that have not been in play for a couple years lead to my desire to ski the corkscrew. Like the group that triggered it, that zone I considered relatively safe and I've skied it a number of times on considerable days without a problem.

With the high wind event beforehand and a pretty stout wind up high that day, no group went higher than the corkscrew, everyone knew it would be slabby up there.

Not wanting to go all the way to the ridge, I punched a skin track a bit lower 3 or 4 turns above the main treeline and changed over in a small group of trees offering protection from the wind. Skinning up we noted no naturals, whooping or shooting cracks. Just before dropping we saw the group that triggered the avy digging a pit.

After the first run I felt pretty confident about the stability of what we just skied, it actually skied pretty shallow, fast and fun. The group that triggered the Avy noted also there increased confidence after the first run.

We decided to hit another treed area mainly because we wanted fresh tracks and the zone we were in was starting to get tracked. With a slightly different aspect, this area was much less wind effected and skied much deeper, I skied a couple very steep but short sections that hardly even sloughed.

I was actually very surprised to read about the indecent later based on how stable the slopes seemed to be definitely has given me something to chew on and think about.

[SchralphMacchio]

Thanks for posting that TBC, good honest discussion. Fear of missing out is strong when you see tracks with no consequences. A big thing to think about, which is statistically unusual, is that in each accident on that day it was the 3rd or 4th skier who hit the trigger point. We never really know how close we are to the edge, even though most of us who like to get after it want to get as close as Mother Nature will allow.

Persistent slabs really are another level of beast to respect.

[adrenalated]

Problem characterization and problem based management of terrain does not feel widespread to me among people I talk to who get after it.

This is an interesting comment. I feel this is the case everywhere I've skied. And if you think about it, dealing with avalanche problems specifically isn't really taught until AIARE L2, and it's uncommon for recreational users to have that level of education.

The mantra in my L2 was "what's the problem, where do I find it, and how do I kill it." With PWLs the answer to that last question is almost always avoidance, which is tough when you're accustomed to dealing with surface instabilities that are easier to manage and present more obvious signs of instability.

[bodywhomper]

It seems that pwl/s even "fool" the pros for various reasons. In CA it's super difficult to teach about it in the field because it's usually not present.

There was a pwl/s that was active in the snowpack during a course that I took years ago in the wasatch (fuac 3 day course that is no longer available). It was really interesting to hear the pros discussing it and hear them describing how they didn't have enough first hand experience with "bridging" to have any confidence.

[Bunion 2020]

Interesting discussion.

Why do all the SAC links go to Steep & Cheap?

[mmmm...pow!]

I'll throw a few point in here.
First, the snowpack right now is in no way anything like what is typically dealt with in a continental snowpack. Continental issues usually involve TG faceting. Our issue is due to surface hoar, which can be found in any snowpack, but seems more likely to cause big issues in more coastal areas where the snowpack piles up deep on top of it. Nothing to do with climate change, either, surface hoar happens here quite often, but usually gets destroyed fairly quick.
As far as decision making, the only way to be 100% safe is to stay off of and away from anything that could potentially slide, meaning anything above ~30*. As has been written on the avy center page every day for the past week or so, often the only way to know if a slope has a week SH layer, and if it is reactive, is for it to be triggered and slide. A pit could be dug in a particular spot and look good, and 30' one way or another the layer might be present and undetected. The snowpack can heal, but it will likely take either a massive dump with widespread avalanches to flush everything out, or over time if the structure wthin the snowpack changes (which might not be until spring melt/freeze cycle).
In the meantime, terrain management is more critical than normal. Avoid terrain traps, and don't assume the skintrack is in a safe spot. The backcountry can be safely skied even in the most extreme avy danger, you just need to know where to go.

[homemadesalsa]

Very interesting discussion. Nicely moderated, Shralp.

Yes, The Avalanche Review would welcome a summary of these two accidents and the issues that they represent, eg noting intermtn issues (surface hoar) in maritime snowpack, McCammon's heuristics/ FACETS (please note that he chose those 5 mostly because they were most common and fit within the pneumonic; there are many more).

I would also welcome a note from TahoeBC about adjusting the day to fit the problem. We tend to focus on when things go wrong, but a view of how real people make decisions that fit the actual problem is important, gives a good pattern to follow.

[swissiphic]

Really good points raised. I live and ski in northwest B.C. and what i've found useful over the past few seasons where p.w.l.'s have been more frequent than long term average has been to develop a personal defined 'permanent green' ski touring run list for times when snowpack structure dictates an ultra conservative approach.