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Avalanche Forecast

Archived

Feb 24th, 2022–Feb 25th, 2022

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

Recently formed 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 speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

A strong ridge of high pressure keeps BC dry until a major weather pattern change takes place beginning this weekend. 

THURSDAY NIGHT: Clear, no precipitation, 5-10 km/h westerly wind, alpine low temperature -12 C, freezing level at valley bottom.

FRIDAY: A mix of sun and cloud, no precipitation, 10-20 km/h southwesterly wind, alpine high temperature -3 C, freezing level at 1000 m.

SATURDAY: Increasing cloudiness with light snow beginning in the late afternoon, 1 cm, 30-50 km/h southerly wind, alpine high temperature 0 C, freezing level at 1500 m.

SUNDAY: Flurries, 3-5 cm, 30-50 km/h southwesterly wind, alpine high temperature 0 C, freezing level at 1500 m.

Avalanche Summary

On Wednesday, a few natural size 1.5 cornice releases were observed on east aspect but did not trigger slab on the slope below. Several natural size 1 to 1.5 from the last few days were also observed in the Coquihalla.

Snowpack Summary

Recent northerly winds have redistributed last weekend storm snow to form reactive wind slabs in lee features and have scoured to the crust in exposed terrain. 

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. 

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

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.