Avalanche Forecast
Issued: Feb 27th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
mconlan,
Avalanche Canada
Slab avalanches will become easy to trigger as the recent snow gains slab properties over a buried surface hoar layer. Wind-affected terrain should be treated as suspect. Assessing for slab properties and conservative decision-making are recommended tactics to avoid the problem.
Summary
Confidence
Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.
Weather Forecast
THURSDAY NIGHT: Cloudy with snowfall in the southern parts of the region, accumulation 2 to 5 cm, moderate to strong southwest wind, alpine temperature -5 C, freezing level 1400 m.
FRIDAY: Cloudy with snowfall, accumulation trace in the north of the region and 5 to 10 cm elsewhere, light to moderate southwest wind, alpine temperature -6 C, freezing level 1000 m.
SATURDAY: Cloudy with snowfall, accumulation 10 to 20 cm, light southwest wind, alpine temperature -8 C, freezing level 900 m.
SUNDAY: Mix of sun and cloud, light west wind, alpine temperature -11 C.
Avalanche Summary
A few small to large (size 1 to 2) wind slabs and a few storm slabs were triggered naturally and by humans on Wednesday. They generally occurred on northerly aspects between 2000 and 2300 m and were 20 to 50 cm thick.The wind slabs were formed from recent wind loading in the northeast of the region and the storm slabs released in the south of the region on the surface hoar layer described in the snowpack summary.
Snowpack Summary
Around 30 to 50 cm of snow overlies a widespread layer of surface hoar that was reported to be between 5 and 15 mm in size. There is uncertainty on whether this layer is a problem in the northern half of the region. In the southern half, this layer exists on all aspects and elevations except for steep, sun-exposed aspects where it was melted by sun and formed a melt-freeze crust. Surface hoar sitting on a thin sun crust may exist on lower angle solar aspects, which is a particularly nasty combination. So far, the overlying snow has been reactive to human activity where the wind has redistributed it, forming a slab. This has been most common around treeline and alpine elevations in the south of the region. A slight warming trend and more snowfall have the potential of activating this layer in all elevation bands.
The mid and lower snowpack is generally well-settled and strong.
Terrain and Travel
- Stick to simple terrain or small features with limited consequence.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Persistent Slabs
Snowfall continues to load a widespread layer of surface hoar, with about 30 to 50 cm overlying it now. This layer has been most problematic in the south of the region. So far, the layer has been most reactive at treeline and alpine elevations, where the recent snow has been redistributed by the wind and formed a slab above the surface hoar.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Strong southwest wind has formed wind slabs in exposed terrain. Use added caution in lee terrain features, particularly near ridges.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 28th, 2020 5:00PM
