Avalanche Forecast

Moderate - Intensity of incoming weather systems is uncertain on Friday

TUESDAY NIGHT: Cloudy with clear periods. Light northwest wind. Alpine low -4, freezing level 500 m.WEDNESDAY: Mainly cloudy. Moderate west-northwest wind. Alpine high -3C, freezing level 1000 m.THURSDAY: Cloudy with isolated flurries, trace to 5 cm accumulation. Moderate to strong west wind. Alpine high 0C, freezing level rising to 1000 m.FRIDAY: Flurries and snow, 5-20 cm. Strong southwest wind. Alpine high +2C, freezing level rising above 1500 m.

On Sunday natural wind slab avalanches were reported on northwest to east aspects. On Friday, a large (size 2) avalanche was observed on a southeast aspect just below ridgeline (MIN report here). Continued cross-loading and variable wind transport has contributed to wind slab development and new slabs may be building on older, harder slabs.A large (size 2) persistent slab avalanche was remote (from a distance) triggered in the Kispiox area on Tuesday. It released over a buried layer of faceted (sugary) snow on a mellower (30 degree slope) southeast aspect at 1680 metres. This avalanche stands out from recent reports for the presence of a persistent weak layer at the failure plane, as well as for its remote trigger on a fairly mellow slope. Although it appears to be an isolated incident, it highlights the presence of a buried persistent weak layer that may remain preserved in northern parts of the region. Images of the slide suggest that wind loading was another contributing factor.

Another 10 cm Tuesday night brings recent snow totals to around 30 cm. A thin crust may be found within the recent snow from a variable mist layer on Sunday. In wind-loaded terrain, wind slabs overly lower density snow. At alpine and high treeline elevations, the recent snow sits on variable surface of wind-affected and faceted snow, and a weak layer of surface hoar in more protected areas. A rain crust/surface hoar combination is found below 1500 m, with warm temperatures settling the snowpack below treeline. Under the new snow interface, 25-50 cm of wind affected storm snow from over a week ago is expected to have formed a good bond with the underlying snowpack. A few buried weak layers that consist of surface hoar faceted snow may exist in some sheltered areas. The upper layer is 35-60 cm deep and a possible culprit in the Kispiox avalanche noted above. The next layer is likely 65-90 cm deep. The lower one is now around 100-150 cm deep.The bottom 30 to 50 cm of the snowpack consists of facets and crusts, particularly in areas where the snowpack is thin. It may be possible for storm slab avalanches to scrub down to ground in thin snowpack areas, resulting in large avalanches.