Avalanche Forecast

High -

Wednesday night: Decreasing cloudy with easing flurries bringing 5-10 cm of new snow. Moderate to strong west winds.

Thursday: A mix of sun and cloud with 3-day snow totals of 25-40 cm and flurries beginning again overnight. Moderate northwest winds easing over the day. Alpine high temperatures around -14.

Friday: Cloudy with snowfall bringing 15-25 cm of new snow, totaling 20-40 cm including overnight accumulations, continuing overnight. Moderate to strong south winds. Alpine high temperatures around -2 with freezing levels reaching 1800 metres.

Saturday: Mainly cloudy with isolated flurries and a trace of new snow.Moderate southwest winds. Alpine high temperatures around -8.

Reports from Tuesday showed the December 27 surface hoar layer described in our snowpack summary becoming very reactive to skier traffic and ski cutting, producing avalanches to size 2 (large) even on quite low-angle slopes and with remote triggers. At that time this layer was buried about 30 cm deep, but the destructive potential of avalanches on this layer has been increasing with snow accumulation forecast to continue through Wednesday night.

Reports from the weekend included several notable MIN reports from the Barkerville area, where shooting cracks, whumphing, and both natural and machine triggered storm slabs were observed failing on the same surface hoar layer, found only 20 cm deep at that time.

Looking forward, dangerous avalanche conditions as described above are expected to persist even as snowfall tapers for Thursday.

3-day snow totals of 25-40 cm are expected to accumulate on the surface by Thursday morning. The new snow has buried a new layer of large surface hoar that was observed in sheltered areas of the region in advance of the storm. This interface may instead present as a thin sun crust on steep, sun exposed aspects.

The new snow adds to 15-30 cm of storm snow from last week. The (December 27) interface below this snow may present as surface hoar on sheltered, shaded aspects, as a sun crust on steep sun-exposed aspects or as a more widespread melt-freeze crust below about 1700 metres. Reactivity at this layer has been noted in recent professional and MIN reports and in some places it may continue to behave as a primary storm slab interface.

A widespread layer of large, feathery, surface hoar from mid-December will likely now be found 90-160 cm deep. Activity on this interface has tapered off, but there is concern for the possibility of storm slab releases to step down to this layer.

A weak layer formed in late November is now buried around 1 m or more below the surface. Concern for this layer is limited to variable snowpack depth areas in the alpine where it most likely exists as a combination of facets and crust.

• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Avoid freshly wind loaded terrain features.
• Avoid being on or under sun exposed slopes.