Snow & Avalanche Discussion
New 24-hour snow totals are in the 4" to 8" inch range with a half to three-quarters of an inch of water. This last little burst of decent snowfall from this storm has increased the avalanche danger. A good amount of avalanche activity to report for the Front Range zone from yesterday provides some evidence.
I was out touring in the drainages north of Berthoud Pass yesterday, and witnessed
a natural soft slab avalanche in Tea Cup Bowl in Current creek (see images below). The avalanche consisted of the storm slab, 1-3 ft thick, approximately 400 ft wide, and ran the length of this small terrain feature; about 150 vertical feet. This is a southeast aspect, 35 degrees, and below treeline at 11,100 feet. Our group also triggered a couple size 1 avalanches in this storm slab near and below treeline on terrain with slope angles in the mid to upper 30s. These occured in fairly forested terrain.
We received
two additional reports from the Berthoud Pass area of skiers triggering and getting caught in storm slab avalanches. A skier triggered an east facing slope at treeline at 11,500 feet above the cliff bands west of pass. The slab was 100' wide and 2-3 feet thick, and ran about 200'. He took a short ride and sustained no injuries. Another skier triggered this same storm slab. He was caught, tumbled, and came to rest on the debris surface with an injured knee. He self-evacuated with two companions. The slab was 2-3 feet deep, almost 1000 feet wide, and ran for 200 feet. We don't have any more details on this slide right now. A natural avalanche also closed Cameron Pass last night.
Observes from across the zone are reporting a very reactive storm slab, that is cracking and sliding under skier weight. The slabs are getting larger in size as the storm snow settles and stiffens. Visibility above treeline was very limited, but widespread natural activity would not be surprising. The snow that fell in the early part of this storm was much lower density than what came later. The storm snow is "upside down", and is not a good structural set up for avalanches. This transition in snow density is easy to see if you dig down, and easier to feel as you move through the terrain. The southwesterly winds have been quite strong along the highest terrain and recent wind deposits are still a concern.
The new snow is heavy, and has added a significant load to our snowpack. We keep inching closer to the point where we can impact those deeper buried weak layers that are still lurking. The small additional weight of a skier can tip this balance. Triggered slides that initiate in the storm wind slab could step down to the deep weak layers to create larger avalanches. This deep slab is scary. It's becoming easier to trigger, and when it releases will produce large and destructive avalanches.
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