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Avalanche Forecast

Archived

Mar 1st, 2023–Mar 2nd, 2023

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

Regions

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

New snow and strong southwest wind may build fresh and reactive wind slabs. Take a cautious approach and investigate the bond between the new snow and the old surface before committing to your line. Keep in mind that if triggered, wind slabs may step down to the deep persistent slab problem resulting in large avalanches.

Confidence

Moderate

Avalanche Summary

No new observations were reported Tuesday.

On Monday, loose dry sluffing from steep terrain was seen as well as a remotely triggered wind slab avalanche size 1.5 that reportedly failed on facets below the recent storm snow.

Last Thursday, two size 3 deep persistent slab avalanches were observed just north of the Hurley summit. One was on a north-facing alpine face and the other an exposed, east-facing open slope at treeline.

Last 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.

Snowpack Summary

Up to 20 cm of new snow should accumulate across the region by Thursday afternoon. This will add to last weekend's storm that brought 15-30 cm of storm snow. In some areas, this new snow has bonded poorly to the stiff wind slabs and near-surface faceting 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

Wednesday Night

New snow 10-15 cm. Alpine temperatures -10°C. Ridge wind southwest 35 to 65 km/h. Freezing level valley bottom.

Thursday

Snow 5 cm. Alpine temperatures -8 °C. Southwest wind 30 to 70 km/h. Freezing level valley bottom.

Friday

Cloudy with sunny periods and a trace of snow. Ridgetop wind 25 to 55 km/h from the southwest. Alpine temperatures -9°C. Freezing level valley bottom.

Saturday

A mix of sun and cloud with isolated flurries. Alpine temperatures near -7°C. Ridge wind northeast 15 km/h. Freezing level valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.