Quick report
Over the past week snowpits have revealed that the persistent weak layer in the bottom of the snowpack is still widespread on W through E aspects, but that failures in this layer are isolated and lack the propogation to result in a large slope release. Confidence in this conclusion will increase with additional observations, but nearly a dozen snowpits in dispersed and concentrated locations have shown similar results. North facing slopes remain the most likely place for an avalanche to occur and shallow areas still show more reactivity than average snowpack depths. For weeks we were on the cusp of a deep slab problem, but now, after settling and melting, most areas, minus deposition zones, are showing the weak layer in the upper 1 meter of the snowpack.
The wind hardened snow in the southern section of big bowl, sundance bowl and much of the Humphrey's cirque made for challenging skinning conditions with 10-15 cms of snow on top of sun crust. This layer often released under the weight of a skier, but lacked the cohesion to slide and fracture in a continuous slab. This led to very small and very isolated releases. In the locations surveyed, this layer failed to form into wind consolidated slabs, mounds or piles. This was likely the result of only light winds affecting the snow during and post-storm and winds generally below ideal transport speedsWeather
- Air Temp
- 33
- Cloud Cover
- clear
- Wind Loading
- previous
- Recent Snowfall
- 8-15
- Snow Avail For Transport
- small smounts
Fair skies and spring-like conditions
Snowpack
The intent of this tour was to observe snowpack structures on upper elevation east and west-facing slopes to determine the presence and reactivity of persistent weak layers buried at and near the bottom of the snowpack, particularly the basal facets from December. In particular, we were interested in the distribution and reactivity of this layer. Of note, the distribution of snowpack depths has shifted in some locations with the high winds of the past 3 weeks. Some slope segments, which were scour zones, have become catchment zones and depths have increased in these locations from from just 50-60 cms to averaging near 100. Depths in deposition zones continue to be over 200 cms. Fewer locations are showing deep slab type conditions as the snow is now more evenly distributed across slopes. Average depths seemed to be between 100 and 130 cms. In the cirque, limited testing showed that the basal facets have grown in thickness and averaged 35-45 cms in width; are no longer enchained but now hollow cups between 2 and 4 cms. Rounds dominated the upper layers of the snowpack, excluding the top 10 cms which were windpacked grains. The bottom layer of depth hoar failed at CT20@40cms above ground with a sudden collapse fracture character. The ECT demonstrated very little propensity for fractures to move through the weak layer resulting in an ECTX. West facing slopes had similar snowpack structure and results. View the snowpilot below and note the CT21@40 SC result and the ECTX result.