On my right: football fields-worth of minutes-old avalanche debris covered the entire valley floor – the same floor that had dominated my view for the past hour and a half, and was uncovered for all of it.
Our tracks and transition zone from the previous run on the slope and flats to the right were wiped out and buried.
It appeared we were on the only 50-foot strip of snow for at least ¼-mile in either direction that had not slid or been buried.
I was convinced there was no way we’d get back to the car without getting tangled in some kind of slide; something terrible had happened, the magic hour had struck, and this mountain was shaking off a layer of 4-5 feet of snow like a dog shakes water from his soaked coat.
Kyle and I were skiing the north side of Tin Can. We’d just done a rather conservative run, skiing down part of CFR ridge, and then dropping north lower down on the ridge where it begins to broaden.Snow conditions below 2500’ were 2-3-feet of heavy and wet toothpaste-like snow with a breakable wet crust on top. Above that, the snow was deeper, dryer, but still dense, with a slight wind or heat crust on the top.
Conditions weren’t great, but they were consistent.
With a hazard rating of moderate for treeline and up, 19 inches of new snow mid-week, and no observed avalanche activity since the prior weekend, if you had asked me what my main avalanche concern for the day was prior to 2:00, I would have said: “wet slide point releases on sunny faces that could run 2-3 feet deep, probably slow and molasses like, but heavy enough to hurt or bury you in the wrong spot.”
That wasn’t a big concern, as our target aspect was northerly/westerly out of any direct sun.
We weren’t thrilled with the snow, but it was nice enough to stay out.
For run 2, after deciding the crowded and sun-baked south side skinner slope looked…crowded and sun baked, and not seeing a compelling reason to not at least try, we decided to poke into one of the north-facing chutes.
Kyle and I were skiing down into one of the western-most chutes, an uncomplicated affair that rolls over like a basketball at the top. We planned to post-up on the exposed ridge that looks down into it – there is no way to have eyes on someone after the chute rolls – but that would be a good enough spot, with the plan that I would head down into the valley below, and radio back up to Kyle as to how it skied. If it was better than what we just did, he would follow, if not, he could head down the ridge, and we would re-group below in the flats near our previous transition spot, and probably just go home.
|A photo showing much of the extent of the 4/17 Tin Can slide, the crown still visible 4 days later following a 2-3 day storm that dropped over 3 feet of snow and delivered triple digit wind gusts. Photo: CNFAIC|
Heading to the exposed rocks overlooking the chute, I couldn’t believe my eyes: It looked like all of Todds had ripped, burying the entire valley floor. For a half second, I thought the debris was still moving, but realized it was static. I could see where it arced out of the chute I was skiing into, as well as maybe those above (east) of it.
Delayed for that second or two, I cut hard back to the ridge line, and started waving in that direction for Kyle to follow.
Four riders had just headed down the ridge as we topped out, and I was convinced there was a burial, maybe multiple, below.
A good full account was compiled by the Chugach National Forest Avalanche Info Center here as to what happened next. (Kyle and I were the party of two that followed the group of 4 that triggered the slide) http://www.cnfaic.org/site/observations/tincan-avalanches-off-the-north-and-south-side-of-cfr-ridge-3/
It’s been a bit of a challenge to make sense of this event.Perhaps one of the most troubling aspects, aside from the narrow margin of time that separated Kyle and/or I from being wiped off the map by this slide, is that it’s been difficult to point to anything in particular that should have warned us of the scope of the danger that day. As a result, it’s not clear that I can say that given the chance to repeat the day, I would have made any decisions differently.
Here are the take aways I’ve landed on so far:
- Deep wet slab on persistent bed surface in late season
- Late season snow: too much too late
- Solar heating
- Consistent, but not great skiing
Here’s what I can say about 1 and 2.
We’ve been dealing with a persistent though stubborn melt-freeze layer since early April that has proved to be a poor bonding surface. A number of large slides have reacted on this layer since the beginning of the month, and given the progression of the season, it’s shown no signs of healing.
It’s pervasive, and exists literally across much of the Kenai range. As a result, its ability to allow slides to propagate on an enormous scale, connecting disconnected terrain features and letting slides go “wall-to-wall” across entire mountain sides, is shocking, and scary. It’s now buried deep under the accumulated snow of early April (12 feet?) (number 3).
When I first began to grasp the scale of the north-side slide, my mind, landed on the Twin Peaks slide that went naturally in 2011 and took out much of the face of that mountain (http://www.cnfaic.org/site/observations/silvertip-creek-twin-tip/). Later, Kyle noted the well-known skier-triggered slide on Sunburst in 2008 (http://www.cnfaic.org/accidents/avy022308.htm), and I think that was a better comparison.
On a smaller scale, in late March 2013, a similar bed surface formed in the Summit Pass region. Snow did not accumulate heavily in the region in the month that followed, however, there was enough accumulation to result in a number of very unpredictable natural and skier-triggered slides through out that zone, though fortunately, because of the overall lack of accumulation, and perhaps the colder temps of that spring, slides were smaller in scale, both in depth and width. Regardless, in light of this season, the lesson learned, was that the persistent weak layer never healed.
The way 1, 2, and 3 blend together, is that we had a nice, heavy, wet layer on top that, in theory, would heal and stick. The lack of avalanche activity the preceding days certainly would have indicated this was occurring. Perhaps, earlier in the season, this is a concept that can be relied on more, but late season, with more daily solar heating, the layers were getting diurnally stressed.
Big dumps to the scale of what we saw this April aren’t uncommon here, but are more typical from late October through late January. Then we have cold days and repeated poundings by violent coastal gales that help glue the snow on to the mountain sides or knock it loose during the heights of the storm cycles, we get good stability.
Ideally, in March through April, good skiing comes from smaller snowfalls (less than 3 feet), and less violent distribution events. Indeed, looking back, the best late season years I’ve known have been characterized by cool springs and a consistent line-up of weak storms.
Looking back on this April, I would describe avalanche conditions as hard to evaluate, and lethal if misjudged.
I think this wording will help stick in my mind. We ski some lines with a lot of risk. I’d like to think we user all the available data to determine if that risk is worth taking. In this case, basically, the data was far too variable.
On number 4, Kyle and I thought we were mitigating the effects of solar heating by skiing a slope out of direct sun. What perhaps we failed to account for in this situation, was the presence of a layer of high, thin clouds, and a nearby storm cell over Portage, that were likely helping to push heat onto all aspects, as opposed to just those in the sun’s cross hairs.
Then there is number 5. I would not have described conditions as extremely variable, so I wouldn’t call this a “system overload situation” (http://atrailcalledlife.blogspot.com/2015/02/avalanche-awareness-false-alarms-and.html), in fact, conditions were rather consistent, just, not good.
What I’m gathering from this, is that my experience levels in the backcountry tend to fall under a rather specific condition set: cold powder. This isn’t surprising, these are the best riding conditions for the most part, and in general, I will seek out and confine myself to the aspects and elevation bands that best support this type of riding condition. As this last comment gets to the point of “duh,” my remark is, in choosing to ski snow conditions that are different (a wet slab, as it was on this day) I should really back up and re-think how I’m making decisions and what criteria I’m using to evaluate stability, and realize that what I may take for granted at other times, may not hold up. More and more, I tend to ask, why even ski in these conditions? That’s harder to answer though after you’ve driven down, skinned up, the sun is out, and the season is drawing to a close.
Thanks to all those that have let me chew on their ears (or screens) to talk this slide out. That pretty well includes everyone I know it seems. I hardly landed on these takeaways on my own, and it was quite distressing feeling like there weren't any solid lessons learned. While its still bothersome that there weren't any big red flags that were missed, I think it can be said there were some situational circumstances that can hopefully be used in the future.