Avalanche Forecast

New Year, New Snow!

Overnight Friday: Cloud cover increasing in the evening, overcast by the morning. Light northerly winds will shift to the west and increase moderate to strong in the early morning. Temperatures rising to -13 C in the alpine. 

Saturday: Cloudy skies with flurries, 5-15 cm of accumulation. Winds strengthening throughout the day, strong to extreme from the southwest. Temperatures rising with an alpine high of -8 C in the afternoon. Overnight the storm will intensify with continued strong to extreme winds accompanying 20-40 cm of new snow, freezing levels rising to 400m.

Sunday: A stormy day. Another 20-40cm of new snow accompanied by strong to extreme southwest winds. Freezing levels rising to 700m by mid afternoon. Continued snowfall overnight with 10-15 cm of new snow accumulation. Winds easing moderate to strong from the southwest.

Monday: The storm will begin to taper. Cloudy with flurries. Moderate southwest winds with another 5-10 cm of new snow. 

On Thursday, size 1 wind slabs where reactive to human triggering in the Whistler area.

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.

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. Today, moderate to strong southwest winds and new snow will continue to transport available snow into fresh, reactive wind slabs in the alpine and treeline.

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. 

• Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
• Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
• Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.