North Columbia

New snowfall is loading numerous buried weak layers, which is reactive to natural and human triggers and producing slab avalanches. Storm slabs could step down to deeper layers and produce large avalanches. Maintain conservative terrain choices.

Moderate - Intensity of incoming weather systems is uncertain

TUESDAY: Cloudy with snowfall, accumulation 10-15 cm, light to moderate westerly winds, alpine temperature near -7 C, freezing level near 1000 m.WEDNESDAY: Partly cloudy with intermittent flurries, light southwesterly winds, alpine temperature near -12 C, freezing level below valley bottom.THURSDAY: Cloudy with snowfall, accumulation 10-15 cm, moderate southwesterly winds, alpine temperature near -8 C, freezing level below valley bottom.

On Sunday, numerous avalanches were triggered naturally and by skiers on the December 15 surface hoar layer at and below treeline on all aspects. The avalanches were small to large, being reported between size 1 and 2.5 with depths of about 40 to 50 cm. This is a consistent trend, with around 5-10 avalanches being reported on this layer each day for the past week.Numerous natural and skier-triggered storm slabs were also noted within the recent 20-40 cm of snow, releasing small to large (size 1 to 2) avalanches at all elevations and on all aspects. Reports of loading in northeasterly lee features were also noted, such as in this MIN post.Please share your recent observations through the Mountain Information Network (MIN).

20-40 cm of new snow has accumulated on surface hoar in sheltered slopes and a sun crust on steep solar aspects. The snow is forming a storm slab that has produced numerous avalanches (see Avalanche Summary). The snow fell with strong southwesterly winds in the alpine, which produced wind slabs in lee features at treeline and alpine elevations. Below treeline, this new snow is mainly a concern in openings (cut blocks, gullies, cut banks).The additional snow has created a dangerous slab above numerous buried weak layers. 40-80 cm of snow overlies layers of weak and feathery surface hoar, which is most often found at and below treeline. This layer has the potential to create easily-triggerable destructive slab avalanches because the layers are buried at a depth prime to human triggering. Snowpack tests are generally showing that this layer could form large avalanches (sudden fracture characters, high propagation potential, rutschblock 1 to 3). See the Avalanche Summary for recent activity. Deeper in the snowpack (90 to 150 cm), a November crust is producing variable test results (sudden to no result). This layer is considered dormant but could be triggered where the snowpack is thin.