Quick report
- Red Flags
- Recent Avalanches, Heavy Snowfall, Wind Loading
- Red Flags Comment
- <p>The new snow was fairly well behaved and I could only get sluffing in the surface. As the winds began to drift snow onto a variety of aspects (although primarily northerly) the fresh wind drifts were sensitive and would easily crack out from your skis.</p>
For this upcoming storm, I am primarily concerned about the following existing layers:
1. The layer of near-surface facets now down 45-75 cms (18-30") underneath the Monday/Tuesday am storm snow. On Monday there simply wasn't enough of a slab to make this layer reactive. Was expecting it to be more reactive on Tuesday given all the new snow, but the storm snow was still not acting as a cohesive slab. However, have been getting easy, clean shears on this layer and the grains are quite weak. I am expecting this layer to be reactive with additional dense storm snow.
2. The Monday/Tuesday am storm snow is very low density and will not support the weight of the 2-3" of water and strong winds.
Sustained southwest winds along the ridges were creating sensitive, fresh wind drifts by mid-day Tuesday.
Outside of wind-affected terrain, the hazard appeared Moderate to me as I could only get sluffing within the storm snow. On steeper slopes with fresh wind drifts, I could easily see a Considerable hazard. Hazard at least Considerable by Wednesday morning, possibly quickly rising to High as dense storm snow accumulates.
If this storm comes in as advertised, I would expect the avalanche hazard to rise quickly during the day on Wednesday. Backcountry travelers really need to pay attention to changing, dangerous avalanche conditions with this next storm.
Snowpack
- Instability Comment
- <p>With so much low density snow to blow around, wind slabs were forming quickly and were sensitive. These are sitting on top of low density storm snow which easily provides a weak layer.</p> <p>Although there was evidence of some natural activity during the storm, the 50 cms (20") of storm snow was manageable and at best I could only produce sluffing in the top 5-10 cms (2-4") of snow. It appears the storm snow was still not acting as a cohesive slab. Dug quite a few quick pits looking at the old snow interface. There is a widespread, preserved layer of near-surface facets that is ~5cms thick (even thicker in some areas) that formed during the clear weather from Thursday through this past Sunday. Monday's No-Name slide likely failed on this layer. On slopes approaching 35 degrees or steeper I was unable to isolate a column (STC) or STV/STE (very easy or easy) clean shears. I think this preserved layer of NSF will be a player in this upcoming expected stormy period.</p>
It seemed from all my samples, there is 50 cm (20") of settled snow from the recent storm. Right-side up with very low-density snow. However, once the wind went to work and began to drift the snow, dense wind slabs began to form, particularly along upper elevation ridgelines.
Saw quite a bit of evidence of sluffing within storm snow, so am guessing upper LCC went through a natural cycle during the storm on Monday or overnight into Tuesday morning,