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Avalanche Forecast

Archived

Jan 24th, 2023–Jan 25th, 2023

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

Regions

Kootenay Boundary, Bonnington, Kootenay Pass, Norns, Rossland, South Okanagan, Ymir, Moyie, St. Mary.

Signs of instability like pinwheeling and tree bombs will clue you into surface layers becoming unstable as temperatures rise on Wednesday.

The first sign of instability at one of our deeply buried weak layers could be a large, destructive avalanche. Choose terrain that won't expose you to the consequences.

Confidence

Moderate

Avalanche Summary

No new avalanches were reported in the region on Monday.

Sunday's avalanche activity in the region consisted mainly of small (size 1 or less) dry loose releases from steeper terrain with skier traffic and ski cutting.

Although persistent and deep persistent avalanches have been on an encouraging decline in the region, forecast warming through Thursday brings real concern for the potential for natural as well as human triggering deep weak layers in the snowpack.

Snowpack Summary

Generally up to about 10 cm but locally up to 20 cm of new snow has buried a new weak layer. It consists of faceted snow as well as surface hoar that has been observed at anywhere from 3 -10 mm in size in sheltered areas up to about 2200 m. On steep solar aspects this interface likely presents as a crust. At higher elevations the new snow has been getting blown around by variable winds and forming wind slabs on a range of aspects as a result.

A freezing rain or rime crust buried on January 18 now sits about 15-30 cm deep.

Additional, locally variable layers of crust, surface hoar, and facets may also be found in the top 30 to 50 cm of the snowpack. These layers have not yet produced widespread avalanches but are being tracked by professionals in the region along with the layers below, which are a more widespread concern.

Layers that are presently a concern include a surface hoar layer developed in early January, down roughy 50-70 cm and a melt-freeze crust from late December that is now down approximately 70-90 cm. These layers are responsible for our persistent slab problem.

Our deep persistent slab problem stems from a weak layer created in mid-November and it is now buried 100 to 190 cm deep. These layers are a major concern and can produce large or even very large avalanches with human or machine triggers.

Weather Summary

Tuesday night

Cloud increasing throughout night, small amount of precipitation in western part of region, winds light to moderate from the Northwest, treeline temps around -6 C.

Wednesday

Mainly sunny. Winds moderate from the Northwest, treeline temps around 0 C. Likely above freezing layer from 1500-2000 m, particularly in the western part of the region.

Thursday

A mix of sun and cloud, nil precipitation, winds moderate from the Northwest, treeline temps around +2 C. Likely above freezing layer from 1500-2000 m, particularly in the western part of the region.

Friday

A mix of sun and cloud, trace precipitation, winds moderate from the Northwest, treeline temps around 0 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.