Avalanche Forecast
Issued: Mar 6th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Slabs that formed from Thursday's storm may take a bit more time to bond to previous surfaces. Cornices are expected to be large and weak.
Summary
Confidence
High - Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
FRIDAY NIGHT: Clear skies, light south wind, treeline temperature -4 C, freezing level 800 m.
SATURDAY: Mostly cloudy with isolated flurries, accumulation 5 to 10 cm, light southwest wind, treeline temperature -5 C, freezing level 600 m.
SUNDAY: Mix of sun and cloud, light northwest wind, treeline temperature -5 C, freezing level 600 m.
MONDAY: Clear skies, light west wind, treeline temperature -5 C, freezing level 800 m.
Avalanche Summary
At the time of writing, we have not received and reports of avalanches post-Thursday's storm. It is expected that many avalanches occurred within the storm snow and potentially the surface hoar layer described in the Snowpack Summary.
Snowpack Summary
Thursday's storm dropped around 20 to 30 cm of snow across the region. The snow fell with strong south to southwest wind, forming wind slabs in lee terrain features.
Around 100 cm of snow overlies a layer of surface hoar on north-facing aspects near and above treeline. Although there have not been and reported avalanches on this layer, it has been found to be reactive in snowpack tests, such as in this MIN and this MIN. This persistent weak layer warrants investigation and a conservative terrain-use strategy until it is clear that it is no longer a problem. Check out the latest forecaster blog that offers a deeper dive into these conditions.
The remainder of the snowpack is well-settled. The snowpack depth varies from around 300 to 400 cm around 1200 to 1400 m and tapering rapidly with elevation, with no snow below 700 m.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Minimize your exposure time below cornices.
Problems
Storm Slabs
Around 20 to 30 cm of recent snow is consolidating into a storm slab in sheltered terrain, which may not bond well to an underlying melt-freeze crust. In exposed terrain at higher elevations, the snow fell with strong southwest wind, forming wind slabs in lee terrain features. These slabs could still be triggered by riders this weekend. Cornices have also likely grown large and could fail from the weight of a human.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer of feathery surface hoar may be found around 100 cm deep on northerly aspects around treeline and alpine elevations. Although we haven't heard of recent avalanche activity on this layer, we have reports of the layer still producing results in snowpack tests. Assess the layer in the snowpack prior to entering committing avalanche terrain or adopt a conservative mindset to avoid the problem.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 7th, 2020 5:00PM
