North Columbia

Another storm wave is keeping avalanche danger elevated in the region. Choose conservative objectives while the new snow settles and bonds to the surface.

Moderate - Intensity of incoming weather systems is uncertain

Thursday: An incoming storm wave will deliver approximately 25cm of new snow. Winds will be moderate gusting to strong from the south. Freezing level rising to 900 metres with alpine temperatures to -6.Friday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light gusting to moderate from the west. Freezing level down to 700 metres with alpine temperatures around -8.Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light from the south. Freezing level dropping to valley bottom and alpine temperatures to -11.

Numerous natural avalanches have occurred in the region and in the adjacent Glacier National Park region in the past 24 hours. Sizes have ranged from 1-2.5, with one report of a size 3 and all activity is attributed to failure at the interface below our storm snow. Continued strong ridgetop winds along with new snow on Thursday will 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, two skier triggered size 2 avalanches were recently reported in the Roger's Pass area. Both are reported to have slid on the mid-December weak layer. Although they took place in an adjacent forecast region and could be considered isolated, a possible pattern of increasing activity on the mid-December layer bears mentioning in the North Columbia region as well.

Between 30 and 80 cm of new snow has fallen since Monday night with the highest accumulations occurring in the Monashees. In higher elevation terrain where the winds were stronger, these accumulations have likely been shifted into much deeper and potentially reactive wind slabs. In areas sheltered from the wind, the new snow is mostly loose and unconsolidated. 50-100cm 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 suggest this layer has been 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.