Storm is here! All avalanche terrain becomes suspect when there is a storm snow problem. Wait for snow to settle and stabilize before going in the backcountry.
The early December crust can be found down 90 to 150 cm below the surface. While activity on this interface has really tapered off, the current storm snow will increase the load on this layer and potentially its reactivity. If triggered, this layer has the potential to be larger than expected, thus being very destructive.
Snowfall is expected to continue until Friday night, bringing up to 40 cm + of low-density storm snow. This will add up to the amount the region received last weekend during the previous storm (20-60 cm). Reactive storm avalanches are expected at all elevations, including loose dry avalanches in sheltered areas and wind slabs in lee terrain at mountain tops. If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
A storm impacting the region offers a nice refresh of cold snow accompanied by strong wind largely out of the south. For the weekend, a ridge of high pressure will strengthen over the BC interior, which will generate strong outflow winds and residual flurries.
THURSDAY NIGHT: Snow 15-20 cm / Freezing level at valley bottom / Moderate southwesterly wind gusting at 50 km/h / Low of -10
FRIDAY: Snow 15-20 cm / Freezing level at valley bottom / Moderate southwest wind gusting at 50 km/h/ High of -10
SATURDAY: Flurries up to 5 cm with another 5-10 cm overnight / Freezing level at valley bottom / Moderate west wind / High of -12
SUNDAY: Cloudy / Freezing level around 500 m/ Moderate west wind / High of -5
Evidence from last weekend's storm was observed again Wednesday, with large avalanches (up to size 2) triggered naturally on alpine feature and small (size 1) loose dry avalanches triggered by riders in steep sheltered terrain. While most of them were reported within the storm snow, few avalanches were released on December crust / facets and produced very large avalanche (size 2,5).
Although this layer has seen more activity in the south and east region (details and photos here) it remains a serious concern for the South Columbias region, particularly as the current storm is rolling in.
Up to 10-15 cm of low-density snow fell during Thursday as the storm has started to impact the region. This new snow is falling on a variety of surfaces: thin sun crust on solar aspects, isolated surface hoar at treeline on sheltered slopes, or fresh wind slabs in lee alpine features at treeline and above. The last storm also brought low-density snow (20-50 cm), accompanied by variable southerly winds.
We're actively monitoring the early December crust. In some places, it's scoured and on the surface, while in wind-loaded terrain features it can be found as deep as 150 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. Avalanches failing on this interface have the potential to be very large.
