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Avalanche Forecast

Archived

Jan 25th, 2023–Jan 26th, 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.

With the rise in temperatures expect to see signs of instability like pinwheeling and tree bombs.

This could create smaller accumulated loading on the surface and trigger weak layers buried further down creating large avalanches.

Choose terrain that won't expose you to the consequences.

Confidence

Moderate

Avalanche Summary

No new avalanches were reported in our region for the last two days.

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. For our neighbours to the north, several wind slab and persistent slab avalanches were reported that ranged in size from one to two.

Although persistent and deep persistent avalanches have been on the decline, warming that is expected to arrive on Thursday brings real concern for the potential for natural as well as human triggering of weak layers buried deeper in the snowpack.

Snowpack Summary

New snow, 10 to 20 cm has buried a new weak layer. It consists of faceted snow, surface hoar (3 to 10 mm), and a crust. The surface hoar is found in sheltered areas up to 2200 m and the crust is present on steep solar aspects. Variable winds at high elevations have pushed this new snow around, creating wind slabs on a variety of aspects.

A freezing rain or rime crust buried on January 18 now sits about 15 to 30 cm deep. More layers of concern (crusts, facets, and surface hoar) can be found in the upper snowpack between 30 to 50 cm down. They have yet to produce avalanche activity but they are something to keep an eye on.

Our main layers of concern include a surface hoar layer developed in early January, down roughly 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

Wednesday Night

Mostly clear with increasing clouds, no accumulation, winds west northwest 15 km/h gusting to 35, treeline temps around 0 C.

Thursday

Cloudy with possible late day sun, up to 9 cm accumulation focused mostly in the western area of our region, winds west 15 km/h gusting to 45, treeline temperatures getting to above 0 C due to a temperature inversion and freezing levels up to 700 m.

Friday

A mix of sun and cloud, up to 7 cm accumulation in some parts of the region ending in the morning, winds northwest 25 km/h, treeline temperatures around -5 C.

Saturday

A mix of sun and cloud, up to 4 cm accumulation, winds northeast 15 to 30 km/h, treeline temperatures -17 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.