A good day to avoid avalanche terrain. Reactive storm slabs are widespread and sit above a complex snowpack increasing the likelihood of triggering large, destructive avalanches over the coming days.
Two surface hoar layers found in the upper 100 cm of the snowpack have been reactive in scattered areas around the region. Be especially cautious around steep openings within and near treeline elevations.
New snow and strong southwesterly wind are building reactive storm slabs, especially on leeward slopes that may see more loading from the wind. Dry loose avalanches and sluffing will likely be seen from steeper slopes and terrain features.
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.
Avalanche activity will likely spike Thursday as the temperatures slightly warm and the winds ramp up, redistributing and consolidating the 60-80 cm of recent storm snow.
On Wednesday the AvCan field team reported a snowmobile-triggered storm slab size 1 from a southwest aspect.
Very few avalanche reports came in on Tuesday. The recent storm snow formed very soft storm slabs with one report of size 1.5 natural. Loose-dry avalanches up to size 1 were seen from steep terrain features.
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 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 more on the potential of triggering deeper weak layers Forecasters' Blog.
60-80 cm of recent low-density storm snow has blanketed the region. The new snow accompanied by strong gusty winds on Thursday will likely form 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.
Wednesday Night
Cloudy with snowfall, accumulation 10 to 15 cm with local enhancements possible. Ridgetop winds 30-40 km/h from the southwest. Treeline temperature -8 °C.
Thursday
Cloudy with lingering flurries in some areas and possible sunny breaks. Ridgetop wind 35 km/h and gusting to 65 km/h from the southwest. Treeline temperature -5 °C and freezing level 1100m.
FridayCloudy with light snow 5-10 cm. Ridgetop wind 30-45 km/h from the South. Treeline temperatures near -4 °C and freezing level 1200 m.
SaturdayCloudy with snowfall, accumulation 5 to 10 cm. Ridgetop wind 25-45 km/h from the southwest. Treeline temperatures warming to -6 °C and freezing level 1000 m.
More details can be found in the Mountain Weather Forecast.
