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Avalanche Forecast

Archived

Feb 22nd, 2023–Feb 23rd, 2023

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

Variable winds may have created reactive wind slabs on all aspects at higher elevations.

The persistent slab problem is not going away any time soon. Choose terrain that has low consequences to manage this problem.

Confidence

Moderate

Avalanche Summary

No new avalanche observation since the weekend. 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.

A week ago, 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 traveling 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

Wednesday Night

Clear, no accumulation, winds northwest 45 to 50 km/h, treeline temperatures -25 ºC.

Thursday

Mostly sunny with increasing clouds in the afternoon, no accumulation, winds west 15 to 30 km/h, treeline temperatures around -20 ºC.

Friday

Cloudy, 5 cm accumulation in the early morning and another 5 cm near the end of the day, winds southwest 25 km/h ramping up to 50, treeline temperatures -20 to -15 ºC and warmer in the alpine.

Saturday

Cloudy with late day sun, 3 cm overnight and another 2 cm accumulation by the end of the day, winds southwest switching to northeast 15 to 20 km/h, treeline temperatures around -15 ºC.

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.