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Avalanche Forecast

Archived

Jan 26th, 2021–Jan 27th, 2021

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

Kootenay Boundary.

New snow and wind in the forecast will mean that fresh wind slabs may build and become increasingly reactive throughout the day.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

TUESDAY NIGHT - Cloudy with clear periods / moderate to strong southeast wind / alpine low temperature near -10

WEDNESDAY - Flurries, 5-10 cm, with another 5-10 cm possible overnight / strong southeast wind / alpine high temperature near -7

THURSDAY - Cloudy with flurries, 5-10 cm, with another 5 cm overnight / moderate southeast wind / alpine high temperature near -4 

FRIDAY - Mainly cloudy with scattered flurries / light to moderate southwest wind / alpine high temperature near -5

Avalanche Summary

Some fresh snow with moderate to strong southeast winds will likely form fresh wind slabs throughout the day on Wednesday. These could be reactive to human triggers in leeward terrain.

A size 1 human triggered wind slab avalanche was reported on a northwest aspect at 2100 m near Whitewater on Sunday. 

Another size 1 human triggered wind slab avalanche was reported on a northeast aspect at 2000 m in the Five Mile Provincial Park area on Saturday. 

Snowpack Summary

5-10 cm of new snow is expected with moderate to strong southeast winds on Wednesday. Pockets of wind slab are expected to form throughout the day at upper elevations.

One or more crusts may exist in the upper snowpack depending on elevation and area within the region. The uppermost crust extends up to around 2000 m. In higher terrain, 15-20 cm of snow may sit over a crust and/or large surface hoar crystals.

Another layer of surface hoar found 20-50 cm below the surface in isolated areas in the north and east of the region appears to be gaining strength but could become more reactive with some new snow in the coming days.

A couple of crusts surrounded by weak faceted grains are buried deep within the snowpack. The upper layer is 80 to 130 cm deep and the lower is near the ground. 

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.