Avalanche Forecast

Archived

Feb 5th, 2022–Feb 6th, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

South Coast Inland.

Avoid avalanche terrain at treeline where triggering a persistent slab avalanche is most likely. High freezing levels and solar radiation could increase the likelihood of triggering.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Saturday night: no new snow expected. Light to moderate west winds with a low of -6 at 1500m.

Sunday: mix of sun and cloud with no new snow expected. Light to moderate west winds. Freezing level rising to 1500 m in the north and up to 2500 m in the south.

Monday: light precipitation throughout the day bringing up to 5cm of snow with moderate west winds. freezing level around 1400m.

Tuesday: trace amounts of new snow with moderate to strong west winds and a high of -3 at 1500m.

Avalanche Summary

On Saturday a size 3 skier triggered avalanche was reported in the Duffy Lake area. Details are limited but we suspect it ran on the persistent weak layer from late January. This avalanche was triggered in a upper treeline feature and showed significant propagation.

In the neighbouring Sea to Sky region, we received a report of a large (size 2.5) human-triggered avalanche near Rainbow Mountain that caught and carried a group of five skiers. The avalanche released on north aspect at 1900 m. It broke 40 cm deep on the late January facet-crust layer. The avalanche propagated across adjacent roll-over features and triggered a sympathetic slide on a small feature 200 m away.

Snowpack Summary

10 to 20cm of recent snow accompanied by strong southwest winds on Friday formed new wind slabs on north and east aspects in treeline and above.

Moist snow will likely be observed on south aspects and all aspects treeline and below.

20 to 50 cm sits above a variety of surfaces including surface hoar, facets and a crust. This layer is most prominent at treeline and above. Especially in the Duffy area.

Terrain and Travel

Be aware of the potential for large avalanches due to the presence of buried weak layers.
Remote triggering is a concern, avoid terrain where triggering slopes from below is possible
Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.

Problems

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.

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.