Avalanche Forecast

The cold before the storm...

Thursday Overnight: Cold and clear. Light northerly winds and alpine temperatures dropping to -20 C by the early morning. 

Friday: Cold and clear. Light northerly winds in the alpine, temperatures increasing throughout the day with an alpine high of -13 C. Strong northerly outflow winds can be expected through Howe Sound.

Saturday: Mainly cloudy with flurries. Temperatures increasing throughout the day as a warm front moves into the region, alpine temperatures reaching -10 C. Winds strengthening moderate to strong out of the southwest. Snowfall intensifying overnight, freezing levels rising to 500m with the potential for 30-40cm of accumulation.

Sunday: A stormy day. Strong to extreme southerly winds will accompany another 20-40 cm of new snow accumulation. Freezing levels rising to around 700m. 

On Tuesday, numerous natural avalanches and cornice failures up to size 2 where observed in the alpine and treeline on a helicopter flight near Whistler. Cold temperatures may have made cornices facetted and weak, highlighting the importance of avoiding overhead hazard and giving them a wide berth when travelling at ridge crest. Cornice failures have the potential to create a large load on the snowpack and trigger deeper persistent weak layers.

Small (size 1) wind slab avalanches were observed on south aspects on Monday as a result of reverse loading from northerly wind. There were also some small human triggered wind slabs over the weekend, including this one from Gin Peak that illustrates how wind patterns earlier in the week have left slabs in atypical locations. With today's northerly outflow winds, we can expect to continue finding reactive wind slabs in unusual locations.

We have been paying close attention to the early December crust, which has formed a persistent weak layer in the region. The last reported avalanche on this layer was on Dec 24, but it produced several notable avalanches around Dec 16 at elevations between 1800-2100 m. This size 2.5 skier-triggered avalanche occurred on a northwest facing slope around 2100 m in the Blackcomb backcountry, and propagated between some shallowly buried rocks.

Learn more about how this persistent weak layer is developing in our latest forecaster blog!

This week, variable winds have heavily impacted the snow in open alpine and treeline terrain, leaving wind slabs of a variety of reactivity and hardness on almost all aspects. In some areas, northerly outflow winds throughout the day will redistribute available snow into fresh, more reactive windslabs. 

This new snow overlies a weak layer of near-surface facets and in isolated areas surface hoar, formed by the persistent cold temperatures earlier in the week. In sheltered areas, up to 30cm of low density, facetted snow can be found.

A weak layer of facets (sugary snow) can be found over a widespread crust that formed in early December (down 60-200 cm). This layer has been most reactive at treeline and low alpine elevations, between 1800-2100 m.

Although we have seen a decreasing trend in avalanche activity on this layer, it has still produced some notable human triggered avalanches over the past week. This problem is particularly hard to predict and poses a tricky low-probability high-consequence scenario (see the problem description and travel advice for suggestions).

The lower snowpack is well settled. Snowpack depth at treeline ranges from 200-300cm. 

• Recent wind has varied in direction so watch for wind slabs on all aspects.
• Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
• Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.