Photo: Fish Eye Guy Photography
Preliminary reports coming out of Montana’s Bridger Bowl do not look good for spring skiers: well-skied runs ripping to the ground. There goes the theory of safety in skier compaction. The avalanches, that occurred yesterday, were results of Bridger Bowl Ski Patrol control work after about 9″ of wet snow and rain. While some results from the wet, heavy snow were to be expected, common runs pulling out to the ground is something else. Good on BBSP for having the foresight to do such heavy control work and preventing any of these monster slides from happening during operating hours. The upper mountain remains closed today as Bridger Bowl management and ski patrol access the situation.
Photo: Fish Eye Guy Photography
WTF? That is sketchy!
this season needs to end already
Im ready for mtb season
dh dh
Brown pow
whoa
God bless ski patrol
Saw this happening on two different locations in Val d isere as early as mid january. Would guess about 230 ft wide and crown at 3.5 ft!!! Really scary stuff
Both avy was not even 100 ft from the slopes… Skied the one location the day before, got a bad feeling after i saw what happened!!
great, now you have to worry in a fucking mogul field??
weird
i was looking at them from the parking lot this morning… crazy… i have a feeling the upper mountain is going to be done for the rest of the season
I’ve got the video:
http://www.youtube.com/watch?v=e3JkJU9I2Vw&feature=youtu.be
BOOM!
my god it went almost all the way to the BOTTOM of the alpine lift… that is a long ways haha… good thing patrol does as much avy work as they do… that woulda been catastrophic if it had happened during the day
Holy F!! That is messed up! Mother Nature sure can be an unruly beast.
Damn nature, you scary! http://www.youtube.com/watch?v=Y45xj38z4pI
Old news – it’s called an “isothermic snowpack” – even groomed runs will slide to ground when iso…this should be common knowledge – it’s a good reason to comply with spring-time run closures. A slope can go from safe in the morning to deadly by early afternoon. There is no theory of “skier compaction safety ” under these conditions.
I guess my assumption (above) was hasty and incorrect. I found the vid of the crown – and it’s not actually true spring iso (as it appeared from the pics) but a full depth uniform slab generated (it seems ??) by iso-promoting conditions (temp and rain) sitting on a final layer of facets at ground.
What say others ??
Hey Chris-
First, thanks for being one of the few people to come back and respond to their own post and offer a correction and further insight- very cool. Indeed, my “theory of skier compaction” was also hasty and a poor choice of words. I guess i was trying to emphasize the presumed safety in a hammered slope.
The activity reminds me a bit of an A-basin in-bounds slide that happened several years ago that took someone’s life. Seemed like similar conditions, but if I recall it was in the afternoon, so perhaps more iso? For the life of me I can’t find the accident report/synopsis.
I haven’t kept abreast of the snowpack development in MT, but if it was anything like the WY/ID pack I have one thought: The cold, high pressure that we experienced during December, combined with a relatively shallow snowpack, allowed depth hoar to form in larger depths than normally experienced. Then, when we finally did get get in the flow the amount of snow we received was enough to heal weak layers within the mid to upper levels of the snowpack, but never enough to ultimately heal the depth hoar.
As a result, there was enough strength in the snow pack (that was essentially a ticking time bomb) to support heavy skier traffic throughout the season. Then, the warm temps combined with precip, was the final stress that allowed the entire snowpack (that was completely consolidated except for the depth hoar) to release?
Just a thought.
Thanks again for your feedback!
The best source for Montana Avy conditions is the Gallitan National Forest Avalanche Center. These guys do great work.
They have both video’s and pictures of the wet slab slides, and do a great job explaining why conditions have developed to their current state. An experpt of the 3/29 report follows, from Mark Staples of the GNFAC. Long but good reading.
Snowpack and Avalanche Discussion:
The Bridger Range:
One week ago a major cycle of big, dry snow avalanches ended and a cycle of wet snow avalanches began. Wet snow avalanches occur every year but usually they are much smaller point releases. This year they were large wet slabs that broke on depth hoar near the ground. This depth hoar was weakened by liquid water in the snowpack. Several avalanches occurred in the backcountry and five, big, wet slab avalanches were intentionally triggered at Bridger Bowl. See photos (page1, page2, page3) and videos (Bridger Gully and Sluice Box) documenting this activity.
Unfortunately last night’s cold temperatures did not freeze the wet depth hoar near the ground, but melting at the snow surface (which supplies liquid water to lower layers) was stopped. Temperatures will climb above freezing again today and slowly melt the snow surface again. This process could accelerate and quickly raise the avalanche danger with intense sunshine this morning or rain this afternoon. Today the avalanche danger is CONSIDERABLE.
The Gallatin and Madison Ranges, the Lionhead area near West Yellowstone and the mountains around Cooke City:
This situation is not much different in other areas which have a similar layer of depth hoar near the ground and some liquid water in the snowpack. The difference is that most other areas have not had as much warm weather as the Bridger Range, thus less liquid water has percolated through the snowpack and weakened the depth hoar. However, the Yellowstone Club Ski Patrol triggered one large, wet slab avalanche on Tuesday on a slope receives strong solar radiation (photo). Near Cooke City the snowpack is especially deep on most slopes and the depth hoar has been insulated from warm temperatures and protected from melting snow. The exceptions are lower elevation slopes with a thin snowpack.
What happens next depends on the weather. Heavy snowfall could simply stress the depth hoar and produce avalanches. Strong sunshine with especially warm temperatures could increase snowmelt further weakening the depth hoar, and produce more avalanches. Heavy rain would do both. Prolonged cold temperatures could re-freeze the snowpack and make it as strong as concrete thus lowering the danger. None of these weather scenarios appears likely in the near term weather forecast and for now we wait to see what happens. For today the avalanche danger is MODERATE. If the sun appears more than expected and temperatures warm rapidly, the avalanche danger will rise to CONSIDERABLE.
Additional thoughts on wet slab avalanches:
Skier or snowmobile compaction doesn’t matter. Avalanches at Bridger ripped out some of the most skier compacted areas on the mountain.
We do not fully understand wet slab avalanches, thus we have a high degree of uncertainty. Also, the consequences of being caught in one of these wet slab avalanches would be fatal. The combination of high uncertainty with high consequences should weigh heavily in our decision making.
Wet slab avalanches are problematic this year because of the depth hoar near the ground. This layer produced many dry slab avalanches. Now it is moist and even weaker.
Small, inconsequential looking point release avalanches can trigger big slab avalanches.
OK we need to pass a law, no weak layers allowed!
Ya, man the f*ck up you layers!.. You’re pathetic..
Nicely done…!