Avalanche Forecast
Regions: Dogtooth, East Purcell, Esplanade, Purcells, West Purcell.
New snowfall and shifting wind will create fresh and reactive wind slabs at upper elevations.
Slabs in motion may step down to deeper weak layers resulting in larger avalanches.
Confidence
Moderate
Avalanche Summary
Since Monday, there have been daily reports of persistent slab avalanches (up to size 2,5) in the Esplanade and Dogtooth Ranges, some being remotely triggered and some being natural. They occurred between 2100 m and 2400 m and ran on the concerning surface hoar layer 40-60 cm deep. Numerous small wind slabs and several large cornices were also reactive to skier traffic on lee alpine features Thursday.
Snowpack Summary
This week brought incremental snowfall, totaling 20-30 cm. Westerly winds have redistributed into deep pockets in lees at higher elevations. This overlies a variety of old layers including a surface hoar layer, sun crust, and wind-affected snow.
A prominent rain crust is found 40 to 60 cm deep and has been reported to extend as high as 2300 m around Invermere and 2000 m around Golden. A layer of surface hoar is also found at this depth and is a particular concern in areas without a thick crust.
The lower snowpack contains large, weak snow grains and in some places a hard crust near the ground. Typical snowpack depths at treeline are 70 to 120 cm, and taper rapidly below treeline.
Weather Summary
Friday Night
Cloudy with 5-10 cm of snow, alpine wind northwest 40 to 50 km/h, treeline temperature -5 °C, freezing level dropping to valley bottom.
Saturday
Mix of sun and clouds, no precipitation, alpine wind northwest 30 to 40 km/h, treeline temperature -10 C.
Sunday
Mix of sun and clouds, no precipitation, alpine wind west 20 to 30 km/h, treeline temperature -8° C.
Monday
Sunny with cloudy periods, no precipitation, alpine wind southwest 20 to 30 km/h, treeline temperature -6° C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
Avalanche Problems
Wind Slabs
Shifting winds and new snowfall will develop fresh wind slabs on leeward terrain and cross-loaded features. Human-triggered are likely near ridge crests and alpine roll-overs. Carefully evaluate your line before you commit to it.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
Choose terrain assuming weak layers capable of producing large avalanches. The layers of concern are a surface hoar layer buried 40 to 60 cm deep and weak facets at the base of the snowpack. Back off if you encounter whumpfs or hollow sounds.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5