Quick report
- Red Flags
- Recent Avalanches, Wind Loading, Poor Snowpack Structure
This probably has nothing to do with backcountry avalanche conditions, but it's just the avalanche geek in me speaking here. I couldn't help to notice that about half the roofs of the houses and condos along the Alta bypass road had avalanched with fresh slides. I must have seen perhaps 20-30 separate avalanches. I'm not sure if I've ever seen that much roof-a-lanche activity after a 1 foot snowstorm without heating by the sun. These occurred on all aspects (I included 4 photos, one from each aspect) so the sun early today probably did not have much effect, especially with the very cold temperatures and mostly cloudy skies. The avalanche in the first photo, I was able to measure the slope steepness at an incredible 23 degrees. I was also able to walk up to the edge of that avalanche and look at the snow structure. I found 1 inch thick, frozen ice crust directly on top of the metal roof and then a foot of low density new snow on top.
I'm speculating that since the storm came in warm and wet, the ice crust formed early and when the cold air arrived, the new snow piled up on top, and the ice crust then froze solid with the very cold temperatures. I'm guessing that most of these slides were glide avalanches, which you would expect, but I was most interested to see that many of them had released very recently, definitely during the day today during the very cold temperatures. The ice crust I examined was well frozen so there did not appear to be any melt water lubrication going on. Almost all of them occurred on metal roofs.
Has anyone else seen this much activity in non-wet avalanche conditions?
Snowpack
- Instability Comment
- <p>The main problem areas are where storm snow and wind drifted snow were deposited on top of weak, pre-existing faceted snow. Of course, we need both a slab and a weak layer to make an avalanche. Many of the weak faceted snow inside the resorts was skied up before the latest storm so there was not a lot of activity except shallower, softer avalanches within the new snow. </p> <p>Several people observed backcountry avalanches today and some broke into faceted snow. I suspect that the main problem areas are where the older faceted snow remained relatively undisturbed before this storm and when combined with storm snow and especially wind deposited snow, it was enough weight to overload the weak layer and make it sensitive. I would continue to avoid the north through east facing slopes above about 9,500' that did not see a lot of skier compaction in the faceted snow before this latest storm, especially slopes with recent wind deposits.</p>
About a foot of low density snow.