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Avalanche Forecast

Archived

Feb 21st, 2023–Feb 22nd, 2023

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

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

Watch for signs of instability as you transition into wind-affected terrain.

The threat from the persistent slab problem still exists and is best managed through low-consequence terrain selection and good travel habits.

Confidence

Moderate

Avalanche Summary

On Sunday, a size 1 wind slab was skier-triggered in a gully at treeline, reminding us that despite great riding in sheltered areas, reactive wind slabs still exist in more exposed areas. See the full report here.

Last Thursday our field team observed debris from a previous large persistent slab avalanche. At least once a week evidence of large persistent slab avalanches is reported. Keep this in mind when travelling in the backcountry.

Snowpack Summary

Up to 30 cm of recent snowfall remains loose and powdery in sheltered areas. In wind-affected areas, variable winds may have created wind slabs on all aspects. This recent snow sits above a decomposing crust up to 5 cm thick that appears to be bonding well to layers above and below. This crust is widespread and found up to 1300 m and as high as 1700 m in isolated areas.

In alpine and upper treeline elevations, a weak layer of surface hoar and facets may be buried about 80 to 120 cm deep on north-to-east aspects. This layer may rest on a harder melt-freeze crust. Where preserved, this layer is capable of producing large avalanches hundreds of metres wide.

Weather Summary

Tuesday Night

Increasing cloud, 2 cm accumulation, winds northwest 40 to 45 km/h, treeline temperatures -15 ºC.

Wednesday

Mostly sunny, no accumulation, winds northwest 40 to 45 km/h, treeline temperatures -20 ºC.

Thursday

Increasing clouds, no accumulation, winds west 15 to 30 km/h, treeline temperatures -20 to -15 ºC.

Friday

Mostly cloudy, 2 cm accumulation in the early morning, winds southwest 65 to 80 km/h, treeline temperatures -20 to -15 ºC and warmer in the alpine.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • The best and safest riding will be on slopes that have soft snow without any slab properties.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

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.