Intense winds will take some of the fun out of the new snow we're getting on Saturday. Fresh wind slabs will start small, but they likely won't bond well with our crusty old snow surface.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Friday night: Cloudy with flurries bringing 5-10 cm of new snow, focused toward the coast. Moderate to strong south winds.Saturday: Cloudy with continuing flurries bringing another 5-10 cm of new snow, continuing overnight. Strong to extreme south winds. Alpine high temperatures around -6.Sunday: Cloudy with scattered flurries bringing 3-7 cm of new snow and new snow totals to 15-25 cm. Flurries decreasing overnight. Moderate southwest winds. Alpine high temperatures around -6.Monday: Cloudy with isolated flurries and a trace to 5 cm of new snow. Light to moderate southwest winds. Alpine high temperatures around -6.
Avalanche Summary
No avalanches were observed in most of the region over the last few days, but on Wednesday in the far north near Ningunsaw, two large (size 2 and size 3) remotely (from a distance) triggered persistent slabs were observed failing over a 20-50 cm-deep layer of surface hoar over crust. This problem is likely isolated to the far north of the region, but may also exist on sheltered high elevation slopes elsewhere in the region. Looking forward, steady light snowfall and high winds will be feeding a new wind slab problem on Saturday. Keep an eye on increasing new snow depths over the day and expect wind slab formation to occur more quickly at higher elevations.
Snowpack Summary
New snow is accumulating above surfaces that range from faceted (sugary) wind-affected snow in wind-exposed alpine areas to weak surface hoar over facets at protected higher elevations to surface hoar over rain crust below about 1500 metres. Below the new snow interface, the wind-affected storm snow from last weekend's storm is expected to have formed a good bond with the underlying snowpack. An exception to this 'good bond' may exist in some sheltered higher elevations that were unaffected by rain during the storm. Here, the old storm snow described above may overlie a weak layer of surface hoar (feathery crystals). This layer was identified as the failure plane in several recent large avalanches in the north of the region. It has not shown in reports elsewhere.For most of the region, a weak layer of facets (sugary snow) buried in early December exists down 180-250 cm. The likelihood of triggering this layer is decreasing, but it could be triggered by humans in shallow snowpack areas, particularly in the north of the region. The potential may also exist for large wind slab avalanches to step down to this layer, resulting in even larger avalanches.
cgarritty,
Avalanche Canada
