Avalanche Forecast
Issued: Feb 28th, 2020 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
astclair,
Avalanche Canada
Winds are strong and shifting direction as snow accumulates, creating a tricky pattern of wind slabs at upper elevations. Use caution around drifted slopes and convex roll-overs.
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
Friday night: Cloudy, 5-10 cm of snow, closer to 20 cm for the Coquihalla, strong southwest winds switching to northwest, freezing level dropping to valley bottom.
Saturday: Mostly cloudy, up to 5 cm of snow, moderate northwest winds, freezing level 1000 m.
Sunday: Mostly clear, light variable winds, freezing level 1200 m.Â
Monday: Partly cloudy, isolated flurries with trace accumulations, moderate southwest winds, freezing level 1300 m.Â
Avalanche Summary
No recent avalanches have been reported. Some minor snowballing was observed on steep, sunny slopes Wednesday and Thursday across the region.Â
On Monday and Tuesday, several small to large (size 1.5-2) natural and human-triggered wind slab avalanches were observed on northeast, northwest, and west aspects in the alpine breaking 10-50 cm deep.Â
Snowpack Summary
By Saturday afternoon, 5-15 cm of snow is forecast to accumulate (with up to 20 cm possible along the Coquihalla) as the freezing level drops to valley bottom. Strong winds from the southwest are expected to switch to the northwest and decrease. This will likely create a complex pattern of reactive wind slabs on lee features at upper elevations.
Earlier in the week, 15-40 cm of snow buried an interface of near surface facets and sun crusts. The surface hoar associated with this interface in other regions reportedly has a more spotty distribution in this region, and it may persist in isolated areas (sheltered open slopes near and above tree line).
In the north part of the region (ie. Duffey/Hurley/Goldbridge), a deep instability exists at the base of the snowpack. It has not produced recent avalanche activity, with the most recent event on February 17. Rapid warming or heavy loading by new snow/wind/rain events has the potential to re-awaken this layer.
Terrain and Travel
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Problems
Wind Slabs
5-15 cm of new snow (up to 20 cm may be possible along the Coquihalla) with strong winds changing in direction (southwest to northwest) may form a complex pattern of reactive wind slabs on leeward terrain features at upper elevations. These areas of concern overlap with where cornices may also be reaching their breaking point.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
In the north of the region (e.g. Duffey, Hurley, Goldbridge), a buried weak layer lingers at the base of the snowpack. This layer has been quiet, with no reports of avalanches on it since mid February. There is potential for it to wake up with rapid warming or significant loading by new snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 29th, 2020 4:00PM
