Avalanche Forecast

Archived

Feb 21st, 2023–Feb 22nd, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

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.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland, Kispiox, Microwave-Sinclair, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

Northeast winds will have generated fresh wind slabs.

Triggering a deep persistent slab remains possible, especially in areas with a thin snowpack..

Confidence

Moderate

Avalanche Summary

No significant avalanches were reported in the past few days but observations have been limited.

Looking forward to Tuesday, we expect fresh, reactive wind slabs to form in a reverse loading pattern and at lower elevations than you might typically expect. These wind slabs may be particularly reactive where they overlie a crust.

On Thursday, there was a report of a natural deep persistent slab avalanche, size two,from the northern part of the region. It was on a northeast aspect in the alpine. Deep persistent slab avalanches like this one continue to be reported at least once a week in shallow snowpack areas.

Snowpack Summary

Monday saw 30 to 40 cm of new snow. This has likely been redistributed by northeast winds in exposed areas at most elevations.

Several layers of facets, crusts/surface hoar can be found in the top 1.5 meters of the snowpack. For the most part, the mid-pack is generally strong.

Weak layers of note from November and December are near the bottom of the snowpack, 150 to 200 cm from the surface.

The total height of snow at treeline is between 200 and 280 cm.

Weather Summary

Tuesday Night

Clear, no accumulation, winds northeast 35 km/h, treeline temperatures, -13 to -18 °C.

Wednesday

Sunny, no accumulation, winds northeast 35 km/h, treeline temperatures -20 °C.

Thursday

Sunny with some clouds, no accumulation, winds northeast 35 km/h gusting to 50, treeline temperatures -23 °C.

Friday

Mostly cloudy, up to 5 cm accumulation, winds west 50 km/h, treeline temperatures around -20 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Keep your guard up at lower elevations. Wind slab formation has been extensive.
Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Avoid areas with a thin or variable snowpack.
Be mindful that deep instabilities are still present and have produced recent large avalanches.

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.