Avalanche Forecast

Avalanche activity has increased with the recent snowfall, rise in temperatures and wind. On Friday several remote avalanches were triggered to size 2, where wind loaded features stepped down to a persistent slab, failing on the December 22nd, December 17th or November 21st layers.

Numerous storm slabs were reported in steep terrain features, naturally and human triggered. As storm slabs sit on a layer of surface hoar, reports noted that conditions were very reactive.

A cycle of natural wind slab avalanches to size 1.5 was observed on Thursday morning, driven by the moderate to strong southeast winds. Two size 2 skier accidentals were also reported in north facing wind affected features, failing on the mid December surface hoar. Read about their decision making after triggering the first avalanche here.

Storm snow accumulates over facets, surface hoar or a crust. Westerly winds are redistributing snow into wind loaded features in treeline and alpine terrain.

The snowpack is becoming increasingly complex with several deeper instabilities that may persist through the season, and sustained cold temperatures have continued to facet (weaken) the snowpack. Layers of concern in this snowpack:

• The latest snowfall sits on a surface hoar layer from late December. Recent reports indicate the storm snow is sensitive to human triggers.

• An early December layer of surface hoar in sheltered areas and a thin sun crust in open south-facing terrain is buried approximately 30-50 cm deep. This layer has recently produced surprising avalanches in upper treeline and lower alpine terrain features.

• The most concerning layer buried in mid November is made up of large surface hoar crystals, facets, and a melt-freeze crust and can be found up to 80 cm deep. This layer has been reactive at treeline between 1700 to 2200 m, on all aspects.

Saturday Night

Cloudy with 5 cm of snow possible. Freezing level below valley bottom. Moderate to strong southwest winds.

Sunday

Cloudy with trace amounts of new snow expected. Moderate westerly winds with a high of -6°C.

Monday

Heavy snowfall returns with 15-30 cm expected over the day and another 5-15 cm overnight. Temperatures warming to or above 0°C as freezing levels rise to 800 m.

Tuesday

Freezing levels climb to 1500 m over the day, moderate southwest winds. Mixed precipitation is forecast, with 10-30 mm of rain or wet snow expected

More details can be found in the Mountain Weather Forecast.

• Use increased caution at all elevations. Storm snow is forming touchy slabs.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.