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Avalanche Forecast

Archived

Feb 25th, 2023–Feb 26th, 2023

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

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

New snow is expected to bond poorly to the underlying surface and form fresh reactive wind slabs in lee areas. What won't be as evident underfoot is the buried hard slabs from this week's northerly winds. Both of these problems are most likely to be an issue in wind-exposed alpine and treeline terrain.

Triggering a deep persistent slab remains possible, especially in areas with a thin snowpack. Sheltered terrain will offer the best and safest riding.

Confidence

Moderate

Avalanche Summary

On Thursday, two size 3 deep persistent slab avalanches were observed just north of the Hurley summit. These slabs are suspected of having failed within the last two days. One was on a north-facing alpine face and the other an exposed, east-facing open slope at treeline. A nearby operation was able to trigger two size 2 wind slabs with a snowcat groomer on northwest-facing terrain at treeline. Skiers were able to trigger small (size 1) wind slabs in alpine terrain on south-to-east aspects in the Birkenhead north of Pemberton.

On Friday, two large (size 3-4) natural deep persistent slabs were observed on south and southeast alpine faces in the Birkenhead. We suspect these slabs occurred as a result of wind-loaded from strong northwesterly winds.

Looking forward to Sunday, fresh and reactive wind slabs are expected to form in lee areas. Keep in mind that older, stiff wind slabs may now be hidden under the storm snow.

For a deeper dive into this week's conditions, check out this awesome South Coast Conditions Report posted by Zenith Guides.

Snowpack Summary

Saturday night's storm will accumulate 10-25 cm of new snow down to valley bottom. This new snow is expected to bond poorly to the stiff wind slabs and near-surface facetting formed by recent wind and cold temperatures.

A melt-freeze crust from late January can be found down 60-80 cm. At the moment this layer appears to be gaining strength though in isolated areas small facets can still be found above the crust.

There is a widespread weak layer of large sugary facets at the bottom of the snowpack. Recent avalanche activity on this layer has been confined to northern parts of the region in the Chilcotins. Snowpack depths around treeline range between 150 to 250 cm.

Weather Summary

Saturday night

Cloudy with snowfall, 5-15 cm of accumulation. Alpine temperatures drop to a low of -10 °C. Light ridge wind from the southwest gusting to 45 km/h. Freezing level at valley bottom.

Sunday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Light ridge wind from the southwest. Freezing level at valley bottom.

Monday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -8 °C. Light ridge wind from the southwest. Freezing level at valley bottom.

Tuesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -8 °C. Ridge wind light from the southwest. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Be especially cautious as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.