Avalanche Forecast
Regions: Sea To Sky.
Isolated 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.
Confidence
Moderate - 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: Becoming partly cloudy, no precipitation, 10-20 km/h southerly wind, alpine low temperature -6 C, freezing level at 700 m.
SATURDAY: A few flurries beginning late in the morning, 3-5 cm, 30-50 km/h southerly wind, alpine high temperature -3 C, freezing level at 1300 m.
SUNDAY: Snow, heavy at times, 25-35 cm, 40-60 km/h southerly wind, alpine high temperature -3 C, freezing level at 1300 m.
MONDAY: Snow, heavy at times, 35-45 cm, 30-50 km/h southerly wind, alpine high temperature -1 C, freezing level at 1500 m.
Avalanche Summary
On Thursday, natural loose dry avalanches up to size 1.5 were observed on steep rocky terrain. A skier also triggered a size 1.5 wind slab on a east aspect alpine slope.
Snowpack Summary
Recent northerly winds have redistributed the snow above the mid-February crust in exposed high elevation terrain which has formed isolated pockets of wind slabs and caused extensive wind scouring. This melt-freeze crust is down around 10-30 cm and reported to exist on all aspects and elevations, except for some of the highest elevation polar aspects. Facets have been observed above the crust on northerly aspects.
The late-January crust/facet/surface hoar interface is buried down 40-100Â cm. This layer was most reactive between 1700 m and 2000 m. 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 with a large load like a cornice or in shallow snowpack areas.
Terrain and Travel
- Be especially cautious 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.
Avalanche Problems
Wind Slabs
Recent strong northerly winds have formed isolated 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: Possible
Expected Size: 1 - 1.5
Persistent Slabs
A weak layer from late-January is down 40-100 cm and was most reactive between 1700 and 2000 m. It is now likely dormant in most areas but still possible to trigger on northerly aspects at upper treeline or lower alpine where the overlying crust from mid-February is thinner and not bridging.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 2 - 3