Avalanche Forecast
Issued: Feb 25th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
ahanna,
Avalanche Canada
A weak layer atypical of this region sits beneath a 30-60 cm thick storm slab. It is most prevalent on shady (north-facing) aspects at upper elevations. Avoid terrain traps and approach convexities and wind loaded features with caution.
Summary
Confidence
Weather Forecast
Tuesday night: Cloudy. Light to moderate west wind. Freezing level 800 m.
Wednesday: Cloudy. Light northwest wind. Freezing level 1000 m.
Thursday: 5-10 cm new snow. Moderate southwest wind. Freezing level 1300 m.
Friday: Mix of sun and cloud. Light southwest wind. Freezing level 1700 m.
Avalanche Summary
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
30-60 cm of recent snow sits over a layer of surface hoar on north-facing (shady) aspects. There may also be areas where the surface hoar sits on a crust, which makes an excellent bed surface for avalanches. Surface hoar is an exceptionally weak layer not often seen in this region. It is expected to persist at least through the week. It is buried deep enough that it is stubborn to human triggers, but may be reactive where overlying snow depths vary due to wind.
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 to no snow below 1000 m.
Terrain and Travel
- Be alert to conditions that change with aspect and elevation.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- Be carefull around freshly wind loaded features.
- Caution around convexities or sharp changes in terrain.
Problems
Storm Slabs
30-60 cm of recent snow is settling into a storm slab over a weak interface consisting of surface hoar, sun crusts or a combination. 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 interfaces will be found on north-facing (shady) aspects in open areas around treeline sheltered from the wind with a clear sky view. A local ski area forecaster shared this advice on Sunday.
Storm slabs will be deepest where strong winds have loaded lee terrain features in alpine and exposed treeline areas. Recent wind has varied in direction from south to northwest, so expect to see wind loading on a variety of lee aspects.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 26th, 2020 5:00PM
