Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells.
Continue choosing low consequence terrain to play in, and avoid steep slopes that are getting a direct hit of morning sun. A complex, and generally weak snowpack is forcing us to find fun on mellow slopes.
Confidence
Moderate
Avalanche Summary
On Sunday, across the region, several small (size 1-1.5) windslab avalanches were reported on various aspects in the alpine and at treeline. They were either triggered naturally, or by the weight of a rider on the slope.
On Thursday, west of Invermere, a large (size 2.5), naturally triggered Deep Persistent Slab avalanche was reported. It was in the alpine, and it's suspected that it was triggered by a combination of windloading, and morning sun warming the slope.
The possibility remains of triggering facets near the base of the snowpack, particularly on shallow, rocky slopes.
Snowpack Summary
20-50 cm of snow since late January is settling, or has been redistributed by moderate southwest wind. Previously reactive windslabs in specific terrain may be starting to bond to the old surface, which may be another layer of windslab, or surface hoar sitting on facets or a thin sun crust.
50-70 cm below the surface, the mid-pack contains a layer buried in early to mid January that remains a concern. It mostly exists as surface hoar, but facets or a crust may also be present.
A layer from late November is found 75 to 150 cm deep and is part of a generally weak, faceted snowpack.
Snowpack depths range between 80 and 180 cm at treeline, with the shallowest depths found on the eastern edge of the region.
Weather Summary
Sunday Night
Mostly clear. No new snow expected. Light to moderate west or southwest ridgetop wind, possibility of strong northwest at very high elevations. Treeline temperature dropping to around -5 °C.
Monday
Mostly sunny, increasing cloud through the day. No new snow expected. Moderate west or southwest ridgetop wind, possibility of strong west at very high elevations. Treeline temperature around -3 °C.
Tuesday
Partly cloudy. No new snow expected. Moderate southwest ridgetop wind trending to strong at higher elevations. Treeline temperature around -3 °C.
Wednesday
Partly cloudy. Possible trace of snow expected. Light to Moderate northwest ridgetop wind. Treeline temperature around -7 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Brief periods of sun could quickly initiate natural avalanche activity.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Approach lee and cross-loaded slopes with caution.
- Uncertainty is best managed through conservative terrain choices at this time.
Avalanche Problems
Deep Persistent Slabs
It remans possible that riders could trigger a weak layer of facets near the base of the snowpack. The most likely area to trigger it is in shallow areas with variable snow depths. Avoid thin and rocky start zones and select routes that avoid traveling through or under large avalanche paths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2.5 - 4
Persistent Slabs
Several weak layers sit in the upper and middle portions of the snowpack are at prime depths for human triggering. Stay disciplined and choose low consequence lines, particularly in steep, wind-sheltered terrain where these layers may be most problematic.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1.5 - 2.5
Wind Slabs
Wind slabs may linger in leeward terrain features, particularly where they overlie surface hoar crystals. If triggered, wind slabs could step down to deeper weak layers.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2