Avalanche Near Aspen Kills Two Backcountry Snowboarders


Post by WildSnow.com blogger | March 14, 2007      

A sad tragedy near here, details pending. For now:

The avalanche happened yesterday afternoon on a peak known as Sunshine/Shimer a few miles east of Aspen. The crown was on a N-NW facing slope around 12,000 feet elevation. One survivor, two dead. According to sources the survivor (who was on skis) said he and his two companions (on splitboards) were still in the skin climbing phase of their day when they were caught. They observed a large avalanche happen nearby, then minutes later they triggered a collapse and subsequent slide in the area where they were skinning.

Black Diamond Verdict backcountry ski
Yesterday’s deadly avalanche near Aspen. Photo provided by WildSnow source in the interest of avalanche safety education.

Sunshine (AKA Mount Shimer) used to be a traditional spring corn ski, but with the advent of snowmobile access on the paved but winter-closed Independence Pass road, Sunshine and other peaks in the area have seen increased winter traffic in recent years. Nonetheless, the farther east you go in the mountains near Aspen (Elks and Sawatch), the thinner and weaker the snowpack generally is during most winters. This winter is no exception, with a stronger snowpack in westerly parts of our mountains, while in the area of Sunshine Peak you’ll find a scary snowpack full of weak layers just waiting for human triggers, and easily weakened during warming trends such as yesterday — especially in the afternoon — exactly when these men were unfortunately there.

Temperature graph
Talk about being in the wrong place at the wrong time. Check out this temperature graph from a snowtell site near the accident. Red line indicates temperature at the time of the accident, which was 48 degrees and spiked! (Image from the Colorado Avalanche Information Center, a government public domain source.)

Interestingly, from a report I received from a source it appears the avalanche victims were attempting to stay in a slightly safer area of sparse trees on the side of a ridge just below timberline. But as is too often the case, when a deep slab triggers, sparse trees do nothing but provide things for you to hit as you’re swept away.

Details of this sad event will come out today. I doubt there is much to learn that we haven’t already heard said a million times. But for locals around here (and visitors) it should drive home the point that skiing or snowboarding an already fragile Colorado snowpack during a time when it’s weakening rather than strengthening is frequently a game of Russian roulette. And one of the most significant weakening factors this time of year is when we get a deep warming event — exactly what was happening yesterday when the avalanche occurred.

This morning’s newspaper report.

Roaring Fork Avalanche Center snowpack evaluation from yesterday explains exactly what probably killed the two men:

RFAC Snowpack Evaluation for March 13, 2007 (yesterday): The warm temperatures and persistent deep instabilities have created a complex snowpack. The recent human triggered avalanches have been sizable and run roughly 2-3 feet deep. These have been a result of deeper instabilities that can be found on many slopes. One layer, located roughly 60-90cm (2-3ft) from the top of the snowpack, has produced very clean test shears in our transitional snowpack. On NW-NE slopes at and above treeline, where the snow has been less affected by the warm temperatures, these instabilities will be more easily trigger. The other element of today’s snowpack quagmire is the increasingly warm temperatures. Last night inversions built, with low temperatures roughly 10 degrees warmer than Sunday night. This brought the overnight freezing line above 11,500ft in some locations, and today’s temperatures will be even warmer than yesterday. At and below treeline and on E-S-W aspects the avalanche danger will raise throughout the day as the chance of natural and human triggered wet activity increases.

Terrain / Travel: Be especially cautions on NW-NE slopes steeper than 30 degrees at and above treeline. Also, natural wet activity will be possible and human triggered slides will be probable on E-S-W slopes at and below treeline as the day progresses. We are at the point of the season when picking your timing on specific aspects is becoming crucial.



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Comments

17 Responses to “Avalanche Near Aspen Kills Two Backcountry Snowboarders”

  1. carl pelleter March 14th, 2007 9:51 am

    My heart sunk when I read this. My prayers go out to all of the family and friends of these individuals. Another tragic avalanche occurred this weekend in the Tetons – my thoughts and prayers go out to all involved in this incident too.

  2. steve March 14th, 2007 9:15 am

    Sorry to hear about this…condolences to all those involved.

    Sounds all too familiar.

  3. Tyler March 14th, 2007 9:41 am

    Always sad to hear about another fatality. How many avalanche deaths have there been this season in CO. It feels like a lot….

  4. Brittany March 14th, 2007 10:26 am

    Thanks for the details Lou. I’ve been trying to find out more information as I know Jason, the survivor. I can only imagine what Jason must be going through and I am not exactly sure who the other victims were, but my heart goes out to everyone involved. This is a terrible tragedy, and I am very sad about it. But the CAIC has been very adamant about reporting to stay off of NW to NE aspects. I suppose we should all head that warning. 🙁

  5. Joel March 14th, 2007 4:10 pm

    It’s deeply painful to hear about another avalanche tragedy. They will continue to occur unfortunately for many reasons, and every time they do, it’s painfully sobering. Fortunately, education and better information from avalanche centers have in my opinion produced a more informed populace in the backcountry. The ratio of avalanche deaths to backcountry visitors has gone way down. From my observations in Colorado, the number of people visiting the backcountry has ballooned dramatically in the last several years, yet the number of fatalities has gone down – way down when you consider how many more folks are in the backcountry. Hopefully that trend continues. Hopefully we can ask ourselves the tough questions and answer truthfully. I’ve been more than lucky more than a few times. Hopefully we can all learn from our mistakes and the mistakes of others.

  6. Scott March 14th, 2007 7:32 pm

    Lou,
    Was this a wet slab? Thanks for doing your part to educate.
    -Scott

  7. Lou March 14th, 2007 7:49 pm

    Scott, I don’t think it was technically what you’d call a web slab. What happens during winters like this is that the slab forms a “bridge” over the weak layers below. So long as the slab remains strong it may support skiers if it’s thick enough, but anything that makes the slab weaker is a 500 square foot red flag. This accident is very reminiscent of the one a few years ago on Highland Ridge, when the guy in the avy class got killed. Weak layers, warming trend, choice to be in the wrong place at the wrong time, etc. And to have all three people caught at once — that really indicates some decision making that exacerbated an already bad situation. Beyond that I hope we hear more facts tomorrow, as I know it’s crass on my part to make too many assumptions.

  8. Lou March 15th, 2007 6:34 am

    Turns out the two men who died were on splitboards, so I edited my blog post to reflect this. My heart goes out to their friends and families — one guy had a child on the way…

  9. Mark Caldwell March 15th, 2007 6:39 am

    Lou,

    Do you think that it’s possible or even likely that they remotely triggered the first large avalanche? They were pretty far away from the first one but how likely that it occurred naturally and coincidentally? Good accident report today on http://avalanche.state.co.us/

    Scary and sad.

    Mark

  10. David March 15th, 2007 12:12 pm

    Lou- this sounds a lot like the conditions that set up the inbounds release at A-Basin (which resulted in a fatality) a year or so ago- a deep weak layer and rapid warming.

  11. Mike March 15th, 2007 2:47 pm

    This accident is also similar to an avalanche fatality in the Tetons the other day. Similar time of day and temperature, although the guys were climbing a SE facing gully. Killed a guy from Steamboat Springs who was climbing with his brother.

  12. Toby March 15th, 2007 4:26 pm

    New to avalanche study I keep seeing that warnings are typically on north facing slopes. Why is this? What makes north facing slopes more dangerous? Are there more typical conditions that make north facing slopes more or less dangerous then south facing slopes? My guess is that it has everything to do with exposure but I would like a more informed explanation.

  13. Milt March 15th, 2007 4:43 pm

    Lou –such a sad story from several angles. Despite the emotion, I’m trying to understand the mechanics better. The official report says the larger avalanche was “remotely triggered by a skier from several hundred feet away.”
    1. Is that an unsually long distance?
    2. How did the large avalanche trigger the fatal, smaller one?
    3. Also, do you have any understanding as to their route and destination?

  14. scott March 15th, 2007 9:12 pm

    Thanks for the explanation, etc.

  15. Brianstory March 18th, 2007 9:32 am

    Toby –

    Yes, in continental snowpacks (like Colorado) weak layers such as surface hoar and depth hoar tend to form on northwest through east facing slopes. These persistent weak layers are often the culprit in the big, fatal mid-winter avalanches. Although really nasty facet/ice crust weak layers are possible on S. facing slopes, the sun on south facing slopes tends to burn off weak layers and discourage depth hoar formation. These are generalizations – do your own avalanche evaluation and play it conservative until you get a good feel for how avalanches work! Also good to consider – in the spring, extended periods of above freezing temperatures tend to turn thin lower elevation snowpacks into isothermal mush which is dangerous and tantamount to torture to slog around in. This (combination of warm temps and a thin snowpack) may have been a contributing factor here. In the spring, it is not uncommon to start out the day in scary, mushy crap snow and climb up into a bomber melt/freeze snowpack near and above treeline. Hope this helps.

  16. Toby March 19th, 2007 5:13 pm

    Thanks Brian, good stuff.

  17. Carla Silvestre August 11th, 2008 12:26 am

    Thanks for the info!

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