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.
|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.
|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.
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 todayâ€™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 todayâ€™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.