Quick report
- Red Flags
- Recent Avalanches, Wind Loading, Cracking, Rapid Warming
- Red Flags Comment
- <p>With the recent wind, there was cracking of the wind slabs and I was able to easily trigger several on small test slopes. I definitely wanted to avoid the larger wind-loaded slopes. With the rapid warming these past couple days, especially with the inversion layer blowing out yesterday, the lower elevation snow got quite damp and there were many wet sluffs of the faceted snow at elevations below about 7,000'. Finally, we have expected heavy snowfall tonight. </p>
Here is a 2-minute video that describes the general snowpack setup for Big Cottonwood Canyon 1/10/2013. Weak near-surface faceted snow is being loaded with hard wind slabs at upper elevations and expected new snow overnight in most locations. It's a complex situation and this should be a good, basic overview.
Snowpack
- Instability Comment
- <p>With the expected heavy snowfall all night, I would expect some of the usual storm snow problems including density inversions and wind slabs within the new snow. As always, monitor the snow carefully as you travel by jumping on small test slopes and regularly digging down with your hand. The new snow is falling on near-surface faceted snow in many areas, which will be especially weak and persistently unstable for several days. Especially in places where either wind drifted snow or the new snow has formed a slab, the avalanches should be especially sensitive and persistent. </p> <p>It's a tricky situation because I suspect that the hazard will actualy be less at higher elevations than mid and lower elevations because the rime on Monday covered up the near-surface faceted snow and the winds before that helped to destroy much of the near-surface faceted snow, while the NSF snow exists intact at mid and lower elevations. So it might be safer up high initially, it may be trickier in the long run because the faceted snow may persist longer under the rime crust. I'm curious to find out....</p> <p>You will have to watch out for wind slabs that were formed before the snow started as well as wind slabs formed within the new snow. The new snow will cover up the old wind slabs making them invisible. They will feel strong and supportable until they break deep below the stout wind slabs on the weak, faceted snow underneath. The wind slabs within the new snow will be easier to detect because they will be right on the surface and you can easily jump on test slopes or dig down with your hand.</p> <p>Bottom Line:</p> <p>Moderate danger rising posibly to Considerable danger depending on how much snow and wind we get with this storm. </p>
Still lots of dry near-surface faceted snow in all areas from the highest peaks to about 7,000'. Below about 7,000 the NSF snow was getting a bit damp. There are old tracks in every imaginable place so we are in dire need of more snow. But the faceted snow on the surface rides quite well if you can find an untracked area. The wind was blowing fairly hard from the southwest, which created areas of wind slabs along the ridges and upper elevation wind exposed terrain. There is some rime crust on top of the faceted snow but it is quite spatially variable.