Avalanche Forecast
Issued: Feb 25th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
dboucher,
Avalanche Canada
Pockets of wind slabs are expected to be still reactive to human-triggering in exposed high elevation terrain, especially where they overlie a firm crust.
Summary
Confidence
Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
A major weather pattern change takes place beginning this weekend. As the ridge of high pressure breaks down, this opens the door to a cascade of incoming Pacific weather systems.
FRIDAY NIGHT: Cloudy with clear periods, no precipitation, 15-30 km/h southerly wind, alpine low temperature -6 C, freezing level at valley bottom.
SATURDAY: Increasing cloudiness with isolated flurries in the late afternoon, 1 cm, 30-50 km/h southerly wind, alpine high temperature -1 C, freezing level at 1500 m.
SUNDAY: Periods of snow, 5-10 cm, 40-60 km/h southwesterly wind, alpine high temperature 0 C, freezing level at 1500 m.
MONDAY: Snow, 10-20 cm, 30-50 km/h southwesterly wind, alpine high temperature -1 C, freezing level at 1500 m.
Avalanche Summary
On Thursday, several natural and human-triggered loose wet avalanches up to size 1.5 were reported on solar aspects. Several natural loose dry avalanches were also observed on steep north-west and east slopes. Finally, a few wind slab avalanches size 1.5 were triggered on east aspect in the alpine.
Snowpack Summary
Recent northerly winds have redistributed available snow to form wind slabs in lee features and have scoured to the crust in exposed terrain. A sun crust is also found at the surface on solar aspects.
A weak crust layer from mid-February is now down around 20 cm in the north and as deep as 70 cm in the south. The melt-freeze crust is reported to exist on all aspects and elevations, except for high elevation northerly aspects in the north of the region. Facets and surface hoar can be found above the crust in the north of the region.Â
A weak crust/facet/surface hoar interface from late-January is buried down 40-100cm. This layer was most reactive between 1700 m and 2000 m in the north of the region. While this layer now appears to be dormant through most of the region, it may still be possible to trigger it at upper treeline or lower alpine features on northerly aspects in the north of the region with a large load like a cornice or in shallow snowpack areas.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Closely monitor how the new snow is bonding to the crust.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Wind Slabs
Recent strong northerly winds have retributed available snow and formed wind slabs in exposed terrain at higher elevations. These wind slabs may be still reactive, especially where they overlie a firm crust.
Aspects: East, South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer from late-January is down 40-100 cm and was most reactive between 1700 and 2000 m in the north of the region. It is now likely dormant in most areas, especially where there is a supportive crust above. In the south of the region, a weak layer from mid-February under the recent storm snow is the more concerning buried weak layer.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 26th, 2022 4:00PM
