Avalanche Forecast
Regions: Sea To Sky.
Recently formed wind slabs are expected to remain reactive to human-triggering in exposed high elevation terrain.
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the extreme variability of wind effect on the snowpack.
Weather Forecast
High pressure remains the dominant weather feature for the rest of the week. The next storm system is currently forecast to arrive on Saturday afternoon or evening.Â
Wednesday Night: Mainly cloudy with light flurries, light to moderate NW wind, treeline low around -12 °C.
Thursday: Sunny, light N wind, treeline high around -4 °C.
Friday: Sunny, light SW wind, treeline high around -2 °C.
Saturday: Increasing cloud cover with light snow beginning in the late afternoon, moderate to strong SW wind, treeline high around -2 °C.
Avalanche Summary
On Tuesday, a natural size 1 wind slab was observed on a west aspect at 2200 m and a skier triggered a size 1 wind slab on a southeast aspect at 1700 m. A natural size 2 cornice release was also observed which did not trigger a slab on the slope below.Â
Three MIN reports from Tuesday describe skier triggered wind slabs in the Whistler area. This report and this report include great photos which show the type of terrain just below ridgelines where wind slabs may be lingering from the recent northerly wind event.Â
On Monday, a natural size 2.5 cornice release was observed on a north aspect at 1900 m which pulled a small slab on the slope below. One natural size 1 wind slab was observed and skiers triggered several size 1 wind slabs. One of these was on a north aspect while the rest were on southeast through southwest aspects.Â
Snowpack Summary
A weak crust/facet layer from mid-February is down around 10-30Â cm. The melt-freeze crust is 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. Recent northerly winds have redistributed the snow above the crust in exposed high elevation terrain which has formed reactive wind slabs and caused extensive wind scouring.Â
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 wind slabs in exposed terrain at higher elevations. These wind slabs may persist longer than normal due to the cold temperatures. Wind slabs may be more reactive 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. It is likely only 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