Quick report
- Red Flags
- Recent Avalanches, Cracking, Collapsing, Poor Snowpack Structure
- Red Flags Comment
- <p>From where we were in the range today we only noticed one avalanche. We experienced some isolated collapsing and cracking within the new storm snow. This happened in a much thinner area that was full of facets near the ground. There are still many areas that are holding a poor snowpack structure. Think anywhere in the range that has already produced avalanches this season, south or west aspects that have a much shallower pack depth. </p>
Photo: 1. The natural wind slab avalanche in Dory Canyon that likely occurred late Thursday or Friday morning during the peak winds and precipitation rates.
Photo: 2. Is an area of much thinner snowpack. We assumed we'd get some collapsing due to the depth and structure, and we did. I isolated a small block of snow and then did a kick turn over the top of it. With a bit of pressure the slab collapsed above the facets and cracked out. Dave Garcia grabbed the photo.
Photo: 3. We had considered getting in to a bit steeper terrain on a SW aspect. Height of snow was 110 cm. We looked at the structure really quickly and preformed two CT's on a 25 degree slope. First CT failed on facets above a crust near the ground upon isolation. The 2nd CT failed on the same facets on the 13th tap. CTM RP Q2. Sheer quality was rough, but we still weren't feeling it and bailed on that option.
I think by tomorrow we will be out of the woods for new snow avalanches. Wind drifted snow will also be less of a concern, if of course , the winds remain light. It's the persistent weak layers in the snowpack that will continue to produce avalanching. Especially in thinner areas or on slopes that have already avalanched this season. It may also, require a larger load on the slope like a snowmobile or two. I'm calling for a moderate danger for persistent weak layer avalanches for tomorrow based on the size and distribution of this problem type.
Forecaster note: This is an excellent observation and I agree with a trend toward Moderate. Storm snow problems have largely dissipated, but there are still wind drifts in the high country that could be sensitive to a skier or rider. Wind slab problems, combined with the unpredictability and destructive force that remains in the persistent weak layer problem, I'm going to keep the danger Considerable on steep, northerly facing terrain.
Snowpack
- Instability Comment
- <p>On slopes steeper than about 35 degree is where I think this problem type lived today. Especially in the upper elevation terrain. We avoided both. By tomorrow I'd think this problem will mostly be gone. </p> <p>On the drive up to the mountain today from town we could see a good amount of snow blowing off of the highest peaks. There is currently no shortage of low density snow to get blown around. We topped out today at about 10,600 where the winds were calm to light. No snow was moving. The weather station on Pre Laurel was reporting light wind speeds ( 1 -16 mph ) today. Those speeds are still strong enough to move low density snow, but we didn't really see that happening. We did see what looked to be an older wind slab that pulled out on a NW aspect at approx. 10,700 feet in upper Dory Canyon. The crown was rounding out and had already partially filled back in. It looked to be roughly 100 feet wide by 2 feet deep. It may have pulled out a small pocket of older snow on a PWL. See photo. This avalanche was large enough to bury, injure or kill a person. D2</p>
The exposed terrain above 10,000 feet had been getting hammered by the south westerly winds on Thursday when I was in this area last. Today you could see the affect those winds had on the snows surface. What was nice powder two days ago was today's wind crusted snow surface. We dropped down a couple hundred feet out of the more exposed areas and found frothy fluff. Late in the day southerly aspects were becoming damp.