Avalanche Forecast

Moderate - Wind effect is extremely variable

Tuesday night: 10-20cm of new snow / Strong westerly winds / Alpine temperatures of about -13Wednesday: 3-15cm of new snow / Strong westerly winds / Alpine temperatures of about -13Thursday: 10-15cm of new snow / Strong southerly winds / Alpine temperatures of about -10Friday: Light flurries / Moderate westerly winds / Alpine temperatures of about -10

No new avalanches were reported at the time of publishing this bulletin on Tuesday. I'm sure there was some natural wind slab activity in response to new snow and wind on Monday night. Continued strong ridgetop winds on Wednesday should promote ongoing wind slab activity. For the short term, I also expect loose dry avalanches to be triggered easily in steep sheltered terrain. Of note, on Christmas day there was size 2 persistent slab avalanche triggered on an east facing alpine feature on the north side of the highway in Roger's Pass. The avalanche, which was reported to have failed on the mid-December weak layer, was remotely triggered from a distance of 30 metres. On Monday, a second size 2 avalanche was triggered by a ski touring party on a southwest facing alpine feature on the south side of the highway in Rogers Pass. The avalanche, which is also thought to have also failed on the mid-December interface, resulted in a partial burial and multiple injuries. Although these seemingly isolated avalanches occurred in a different forecast region, these events may point to a pattern of increased activity on the mid-December layer which may also extend into the South Columbia region.

By Tuesday afternoon, between 25 and 65 cm of new low density snow had fallen with the highest accumulations occurring in the Monashees. In higher elevation terrain where the winds were stronger, I'd expect new wind slab formation on lee features. In areas sheltered from the wind, the new snow is mostly loose and unconsolidated. 50-90 cm below the surface you'll find the mid-December interface which consists of wind affected snow, faceted (sugary) crystals, and/or surface hoar crystals. Recent tests suggest the the new snow is well bonded to the interface in most areas. However, this layer is still reactive in some snowpack tests and should be investigated before pushing into steeper terrain. Limited observations from the North Columbia region suggest this layer may be especially touchy on the eastern side of the Selkirks. The thick mid-November crust layer typically sits 1-2 m down in the snowpack. Recent test results on this layer suggest it is generally well bonded to the adjacent snow with the possible exception of shallow snowpack areas. This layer is considered dormant at this time but remains an isolated concern that we will likely be tracking through much of the season.