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Avalanche Forecast

Archived

Jan 23rd, 2022–Jan 24th, 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 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

Northwest Coastal.

Continue to make conservative decisions. As the freezing level rises persistent weak layers could become more sensitive to rider triggering.

Confidence

Moderate -

Weather Forecast

Sunday night: freezing levels falling to 600m around midnight. Light rain turning to snow with light to moderate southwest winds.

Monday: Partially cloudy. Freezing level rising to 2500m. Light southwest winds with no precipitation expected. 

Tuesday: Mainly cloudy, light precipitation. Freezing level around 1000m. Light to moderate southwest winds. 

Wednesday: some light precipitation with light winds. Freezing levels around 900m.

Avalanche Summary

On Saturday a size 1 skier remote was reported on a northeast aspect at 1200m. This avalanche failed while a group was skiing on a supported feature with steeper terrain adjacent to them. It failed on a surface hoar layer. This avalanche is a good indication of the sensitivity to triggering.

On Friday, operators north of Terrace reported several skier-remote wind slab avalanches size 1.5-2.5 that failed on a surface hoar layer.

On Thursday, numerous natural, human-triggered, and remote-triggered storm slab avalanches up to size 2.5 were observed throughout the region. A buried layer of surface hoar, and below 1300m a thick melt-freeze crust likely contributed to the reactivity and wide propagation of these storm slabs.

Snowpack Summary

Last week's storm brought up to 50cm of snow with warm temperatures, building a denser slab above a weak layer of buried surface hoar and a thin melt-freeze crust below 1300 m. The presence of these weak layers means reactivity might persist for longer than usual. In wind loaded areas, associated strong southwest winds have created wind slabs in lee areas.

A layer of sugary facetted grains may be found about 80 to 130 cm deep, which formed during the cold spell in late December to early January. To date, this layer has only been problematic in the northern half of the region.

The remainder of the snowpack is strong in the south of the region. In the north of the region, the base of the snowpack consists of faceted grains around a melt-freeze crust, which is currently dormant.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Be careful as you transition into wind affected 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.