Avalanche Forecast

Archived

Feb 23rd, 2023–Feb 24th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

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.

New snow and moderate winds may produce reactive wind slabs.

The persistent slab problem remains a concern. Choose terrain that has low consequences to manage this problem.

Confidence

Low

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

The new snow that arrived Thursday night will be falling on wind slabs on all aspects at higher elevations due to recent variable winds. Approximately 30 to 50 cm down a decomposing crust, up to 5 cm thick, can be found. It appears to be bonding well to layers above and below and is widespread up to 1300 m and isolated as high as 1700 m.

A weak layer of surface hoar and facets may be buried about 90 to 140 cm deep on north-to-east aspects. This layer may rest on a harder melt-freeze crust. Where preserved, this layer, if triggered, is capable of producing very large avalanches.

Weather Summary

Thursday Night

Cloudy, up to 7 cm accumulation by morning, winds southwest 25 to 30 km/h, treeline temperatures around -20 ºC.

Friday

Cloudy with possible sunny breaks late in the afternoon, 5 cm accumulation late in the day, winds southwest 20 km/h, treeline temperatures -20 to -15 ºC.

Saturday

Cloudy with late day sun, up to 5 cm accumulation, winds north 15 to 20 km/h, treeline temperatures around -15 ºC.

Sunday

A mix of sun and cloud, trace accumulation, winds northeast 35 km/h, treeline temperatures -17 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.
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.