Avalanche Forecast
Issued: Mar 7th, 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. Should the clouds clear, sun-exposed slopes could rapidly weaken and looming cornices could fail.
Summary
Confidence
High - Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
SATURDAY NIGHT: Partly cloudy, light southwest wind, treeline temperature -5 C, freezing level 500 m.
SUNDAY: Mix of sun and cloud, light northwest wind, treeline temperature -5 C, freezing level 600 m.
MONDAY: Clear skies, light northwest wind, treeline temperature -4 C, freezing level 800 m.
TUESDAY: Cloudy with snowfall, accumulation 5 cm, moderate southwest wind, treeline temperature -2 C, freezing level 900 m.
Avalanche Summary
Many small storm slab and loose avalanches were triggered naturally and by skiers on Friday. This occurred within the storm snow that fell on Thursday.
Avalanche activity is expected to decrease as the storm snow bonds to underlying surfaces. Naturally avalanche activity is unlikely, unless the sun comes out and rapidly warms up the snow. Human-triggered avalanches remain possible within the storm snow and potentially the surface hoar layer described n the Snowpack Summary.Â
Snowpack Summary
Thursday's storm dropped around 20 to 30 cm of snow across the region. The snow has consolidated into a slab that reportedly did not bond well to underlying surfaces. This snow is likely slowly gaining strength. The snow fell with strong south to southwest wind, which formed 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 some snowpack tests. 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
- The new snow may require another day to settle and stabilize.
- Be careful as you transition into wind affected terrain.
- Minimize your exposure time below cornices.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
Problems
Storm Slabs
Around 20 to 30 cm of snow fell on Thursday, which may still be gaining strength. Storm slabs could be triggered in steep features, particularly where it overlies a melt-freeze crust. When the sun shows its face on Sunday, the storm snow on sun-exposed slopes could rapidly deteriorate. Thursday's snow fell with strong southwest wind, which formed wind slabs in lee terrain features. These slabs could still be triggered by riders, particularly immediately adjacent to ridges. Be aware that 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 some 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 8th, 2020 5:00PM
