Avalanche Forecast

On Saturday a few natural and one skier remote size 3.5 deep persistent slab avalanches were reported. These avalanches all released around 2500 m and on easterly aspects. This MIN shows some large naturally occurring deep persistent slab avalanches. These avalanches likely occurred middle of last week.

On Wednesday a fatal avalanche incident involving a group of skiers occurred in the Purcell Mountains west of Invermere BC. The size three avalanche was triggered on a southwest facing slope at 2500 m. The weak layer of facets buried in late November That sits at the bottom of the snowpack was responsible. Very large avalanches failing on this layer are most likely to be triggered in shallow rocky terrain with variable snowpack depths at upper treeline and in the alpine.

Early last week several skier triggered avalanches were reported. Two of these avalanches were remotely triggered. Surface hoar layers from January and February were initially triggered. In one case the avalanche then stepped down to the facets at the bottom of the snowpack. These avalanches occurred at treeline and above and on a variety of aspects.

The purcells are likely to continue to see very large destructive avalanches failing on the basal facets from late November. While we are seeing less avalanche activity in the Rockies side of this region the potential for these type of avalanches remains there as well.

Up to 40 cm of storm snow from earlier in the week sits over wind affected surfaces. Expect deeper deposits on north and east facing slopes, from previous west through south winds. Wind slabs may be found on all aspects due to variable winds in the past couple days.

Buried surface hoar sits 30-60 cm deep in sheltered terrain features, and a thin sun crust exists at the same depth on steep south-facing terrain. Several other layers from January can also be found in the top 100cm of the snowpack.

The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. this weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.

Sunday Night

Cloudy with the possibility of light flurries bringing up to 5 cm of new snow. Light to moderate easterly winds shifting to light westerly by the morning. Low of -17°C at 2000 m.

Monday

A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light southwest winds and a high of -7°C at 2000 m.

Tuesday

Mostly sunny with the possibility of light flurries bringing trace amounts of new snow. Light southwest winds and a high of -7°C at 2000 m.

Wednesday

Mostly sunny with no new snow expected. Light southeast winds and a high of -5°C at 2000 m.

More details can be found in the Mountain Weather Forecast.

• Avoid areas with a thin or variable snowpack.
• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Remote triggering is a concern, watch out for adjacent and overhead slopes.
• Avoid exposure to steep sun exposed slopes.