Avalanche Forecast
Issued: Feb 27th, 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
A weak layer atypical of this region is buried 30-60 cm deep. It is most prevalent on north-facing aspects near treeline and may become more reactive as new snow accumulates. Avoid terrain traps, and approach deeper drifted areas and convex roll-overs with caution.
Summary
Confidence
Weather Forecast
Thursday night: Cloudy, up to 5 cm new snow, light to moderate southwest winds, freezing level 1300 m.
Friday: Mostly cloudy, 5-10 cm of snow above 1200 m, southwest winds increasing to strong by end of day.
Saturday: Cloudy, 15-25 cm new snow, southwest winds decreasing from strong to light by end of day, freezing level dropping below 1000 m.
Sunday: Mostly clear, light variable winds, freezing level 1000 m.
Avalanche Summary
No new avalanche observations. This MIN post from Monday reports a skier triggered size 1 wind slab in the alpine, suspected to have run on surface hoar. Explosive control work conducted Monday produced size 1-1.5 storm slabs running on a crust.
Snowpack Summary
By Friday afternoon, 5-15 cm of snow is forecast to accumulate. Strong winds from the southwest will likely drift the new snow into touchy wind slabs on lee features at upper elevations and may bring cornices to their breaking point.
30-60 cm of recent snow sits over a layer of surface hoar on north-facing aspects. Surface hoar is an exceptionally weak layer not often seen in this region. There may also be areas where the buried surface hoar sits on a sun crust, which makes an excellent bed surface for avalanches.
The remainder of the snowpack is well settled. Depth varies from around 250 to 300 cm at the peaks of the North Shore mountains (1400 m), tapering rapidly with elevation. Little snow exists below 1000 m.
Terrain and Travel
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Problems
Wind Slabs
5-15 cm of new snow accompanied by strong southwest winds may form 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: North, North East, East, South East, South, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
30-60 cm of snow overlies a weak interface of surface hoar, sun crusts, or a combination of the two. This is not typical of this region and will take longer than usual to heal. It is expected to persist at least through the week. The most problematic areas are north-facing open slopes near treeline. Loading from new snow and wind may increase reactivity.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 28th, 2020 4:00PM
