Conditions may have improved, but be mindful that deep instabilities are still present. Avoid shallow or variable depth snowpacks and unsupported terrain features.
Recent wind slabs have been reactive where it overlies surface hoar. Along with suspect layers in the upper snowpack, expect to find lingering wind slabs on wind-affected slopes at higher elevations, and anywhere a slab forms over crust or surface hoar layers.
The early December crust can be found down 100-150 cm below the surface, with weak sugary crystals (facets) on top of it. Large avalanches have been observed at all elevations including some unusual areas such as the middle of slide paths, open trees, and burns. Although the likelihood of triggering an avalanche is decreasing, there is ongoing concern for smaller avalanches stepping down to this layer.
A variety of snow surfaces can be found: crusts at lower elevations and on solar slopes into the alpine, wind press and wind slabs in open and exposed terrain, and dense powder in sheltered areas. Surface hoar growth has also been reported.
The most recent snowfall covered a layer of surface hoar now down 20-30 cm, this interface was responsible for the most recent natural storm slab avalanches reported Jan 20-21. The top 50-100 cm of the snowpack has a variety of little layers that may or may not be a problem. These layers include surface hoar and crusts from January snowfalls and facets buried at the start of January.
The primary weak layer that remains a widespread concern across the Columbia Mountains is a deeply buried crust/facet layer that formed in early December. It is typically down 100-150 cm, but as deep as 200 cm in wind-loaded terrain. There has been regular avalanche activity on this layer at all elevations for over a month, but we are now seeing decreasing evidence since the last warm event.
MONDAY NIGHT: Partly cloudy / Light northwest wind / Low temperature -10 C / Freezing level dropping to valley bottom.
TUESDAY: Cloudy with sunny periods / Light southwest wind / High temperature -6 C / Freezing level around 700 m bottom.
WEDNESDAY: Cloudy with sunny periods / Increasing westerly wind gusting 40 km/h / High temperature -8 C / Freezing level at valley bottom.
THURSDAY: Mix of sun and clouds / Increasing southwest wind / High temperature -8C / Possible temperature inversion / Freezing level at valley bottom.
On Sunday, numerous cornice falls were reported in the south part of the region, with some triggering storm slabs avalanches up to size 2. Wind slabs are still showing signs of reactivity throughout the region, producing large natural avalanches (size 2) as well as surprising human-triggered avalanches. In some cases, a weak layer of surface hoar was reported at the interface (down 30-60 cm).
During the warming event Saturday, explosives near the Trans Canada triggered very large avalanches (size 2.5-3.5) failing on the early December facet/crust layer. This included a historical size 4.5 avalanche which started at ridgeline, created new trim lines, and destroyed mature timber.
The past week, numerous very large (size 2.5-3.5) deep persistent slab avalanches occurred in both the Selkirks and Monashees. These avalanches failed on the early December facet/crust layer, typically 100-150 cm deep. One notable pattern is that many of these avalanches released at relatively low elevations (1700 to 2000 m) in open clearings, burns, and slide paths. In many cases, they were triggered by smaller avalanches starting at higher elevations. This layer is likely to plague our snowpack for the remainder of the season and will be a low probability but extremely high consequence result if triggered.
