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Avalanche Forecast

Archived

Feb 23rd, 2022–Feb 24th, 2022

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

Regions

Kootenay Boundary.

Pockets of wind slab likely linger on various aspects in exposed terrain and around ridgelines. 

There is recent evidence that the persistent avalanche problem can still be human triggered in parts of the region.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

WEDNESDAY NIGHT: Trace of snow possible, light westerly winds. Alpine low of -16. 

THURSDAY: Mix of sun and cloud, light northerly winds and alpine high of -7.

FRIDAY: Partly cloudy, light westerly wind and high of -8.

SATURDAY: Mostly sunny, moderate southwest winds, alpine high of -4.

Avalanche Summary

On Tuesday a backcountry user near Whitewater was able to trigger small wind slabs near ridgecrest and found better riding in lower, more sheltered terrain. Explosives control in the region was able to trigger wind slab avalanches in the size 1.5 range. On Monday there were several size 1-1.5 wind slabs triggered by skiers as well as a few natural wind slabs spotted in the backcountry. Surface hoar layers buried in January have also been implicated in two recent size 2 avalanches in the region. 

Snowpack Summary

Recent northeast winds have scoured and wind-affected open areas forming wind slabs in lee terrain. This reverse loading means there may be wind slabs in unusual places. In sheltered locations, there is likely around 20-40 cm of snow over an old February drought layer interface that consists of various melt-freeze crusts and old wind-pressed snow depending on your elevation and aspect.

Two layers of buried surface hoar sit in the upper snowpack and are likely most reactive in sheltered areas at treeline. These are now down around 40-50 cm and 50-70 cm deep. Though improving, these layers remain reactive in some snowpack tests and have been responsible for sporadic avalanches, including a recent size 2 that was triggered remotely by a skier walking on a ridge.

The lower snowpack is well consolidated, with a crust/facet layer found 100 to 200 cm deep. It is currently considered dormant, but could become active later this season. Check out the forecaster blog for more information. 

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

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.