Avalanche Forecast
Issued: Feb 29th, 2020 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
astclair,
Avalanche Canada
Wind-drifted snow at upper elevations is the primary concern for the region on Sunday. In the north, buried weak layers will require careful evaluation and terrain selection. Ice climbers be wary of periods of strong sun.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Saturday night: Mostly clear, light northwest winds, freezing level dropping to valley bottom.
Sunday: Mostly clear, increasing cloud in the afternoon, light variable winds, freezing level 1000 m.Â
Monday: Partly cloudy, isolated flurries with trace accumulations, moderate southwest winds, freezing level 1300 m.
Tuesday: Mix of sun and cloud, scattered flurries in the afternoon with up to 5 cm of accumulation, strong southwest winds, freezing level rising to 1500 m.
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 1-2) 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
20-30 cm of snow has accumulated since Friday, with 30+cm in the south of the region (i.e. Coquihalla). Strong winds from the south switched to the northwest and decreased. The winds redistributed the storm snow into a complex pattern of reactive wind slabs on lee features at upper elevations and rapidly loaded cornices. Periods of sun on Sunday are expected to initiate pinwheeling and rollerballs from strong solar radiation on steep, sunny slopes. Ice climbers should monitor for the effect of solar radiation on overhead snow and for the potential for small loose wet avalanches to have consequences.
Buried 40-70 cm deep, a weak layer of sugary faceted snow and feathery surface hoar from February 22 may persist and warrants careful evaluation, particularly in the northern part of the region (i.e. Duffey/Hurley/Goldbridge). On south-facing slopes, this weak layer may be combined with a melt freeze crust. Check out the latest forecaster blog that offers a deeper dive into these conditions.
Also in the northern part of the region (i.e. Duffey/Hurley/Goldbridge), a deep instability exists at the base of the snowpack. It has not produced recent avalanche activity since February 12th. Rapid warming or heavy loading by new snow/wind/rain events has the potential to re-awaken this layer.
Terrain and Travel
- 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.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Wind Slabs
20-30 cm of recent snow with strong winds changing in direction (from south to west to northwest) has formed 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
Persistent Slabs
In the north of the region (e.g. Duffey, Hurley, Goldbridge) on sheltered slopes near and above treeline, a layer of surface hoar from February 22 may be buried under 40-70 cm of snow. On solar aspects, these weak grains may be accompanied by a crust. Recent snow, wind, and solar radiation may have promoted cohesion in the slab above this layer, priming it for human triggering. Travelling near steep, open slopes at upper elevations warrants an investigation of this layer.
Deeper in the snowpack, a weak layer of facets near the ground presents a lingering concern on steep, shallow slopes in the alpine.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 1st, 2020 4:00PM
