Stormy conditions continue with localized enhanced snowfall amounts. New storm slabs will build over a complex snowpack increasing the likelihood of triggering large, destructive avalanches over the coming days.
Two surface hoar layers found 30 to 80 cm deep have been reactive in scattered areas around the region. Be especially cautious around steep openings within and near treeline elevations.
New snow and strong westerly wind are building reactive storm slabs, especially in leeward terrain features that may see more loading from the wind. The new snow may overly lingering wind slabs that formed last weekend from northeast wind. Dry loose avalanches will likely occur from steeper terrain.
A layer of large and weak facets sits near the base of the snowpack. This layer continues to produce very large avalanches that can travel far. The likelihood of natural and human-triggered avalanches will increase as snow accumulates. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer.
Natural avalanche activity is expected on Wednesday due to new snow combined with blowing ridgetop wind.
One natural wind slab size 2 was reported on Monday at 2200 m.
Last weekend, several very large (size 3 to 4) avalanches were triggered naturally on the basal facets. The avalanches were on all aspects and generally in alpine terrain between 2400 and 2900 m. See here for a video of a rider-triggered avalanche near Renshaw and another example here near Clearwater.
These avalanches are similar to what we've seen over the past week, with persistent and deep persistent avalanches releasing on all the weak layers described in the Snowpack Summary. Most avalanches over the past week were large to very large (size 2 to 4), occurring between 1700 and 2400 m and on all aspects. See this MIN for a recent example and see here for information on a fatal skier-triggered avalanche incident from last week near Revelstoke.
See more on the potential of triggering deeper weak layers Forecasters' Blog.
25 cm of new snow and strong westerly wind will form new and reactive storm slabs and wind slabs in lee terrain features. They will overly previously wind-affected snow from recent northeast wind.
Two layers of surface hoar crystals and/or a melt-freeze crust may be found around 30 to 80 cm deep. Surface hoar is most likely found in wind-sheltered terrain around treeline and lower alpine elevations. The melt-freeze crust is found up to 1800 m on all aspects and into the alpine on sun-exposed slopes.
Large and weak facets from November are near the base of the snowpack, which continue to produce very large avalanches in the region.
Tuesday Night
Cloudy with snowfall, accumulation 10 to 20 cm with local enhancements expected. Ridgetop winds moderate from the West. Treeline temperature -12 °C.
Wednesday
Cloudy with snowfall, accumulation 10 to 20 cm with local enhancements possible. Ridgetop wind light to moderate from the southwest. Treeline temperature -10 °C.
ThursdayCloudy with snowfall, accumulation 10 to 20 cm with local enhancements possible. Ridgetop wind moderate from the southwest and temperatures near -10 °C.
FridayCloudy with snowfall, accumulation 5 to 10 cm. Ridgetop wind light from the southwest. Treeline temperatures warming to -6 °C.
More details can be found in the Mountain Weather Forecast.
