Avalanche Forecast

Archived

Feb 10th, 2020–Feb 11th, 2020

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

Cariboos.

New snow accumulation overnight Monday and through Tuesday combined with moderate to strong winds will continue to promote wind slab development at upper elevations. As a result, wind slabs continue to be the main concern.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Forecast snowfall amounts are uncertain.

Weather Forecast

Monday Night: Cloudy with scattered flurries, accumulation 5-10 cm. Moderate west wind. Alpine high temperatures around -8.

Tuesday: Scattered flurries, accumulation 5 cm. moderate to strong west wind. Alpine high temperatures around -5.

Wednesday: Mix of sun and cloud. Light southwest wind. Alpine high temperatures around -8.

Thursday: Flurries. Light to moderate southwest wind. Alpine high temperatures around -7.

Avalanche Summary

Reports of new avalanche activity on Sunday were of skier or rider triggered wind slabs to size 1 and 1.5 in the alpine and at tree line.

There was a report of a remotely triggered (from a distance) size 2.5 deep persistent slab avalanche on Saturday. It was 130 cm deep and triggered in a shallow area at 2300 m on an east aspect.

Snowpack Summary

20-60 cm of snow from the last week overlies previously wind-affected snow at higher elevations, with diminished depths of about 20-30 cm above a widespread melt-freeze or rain crust up to about 1700 metres. This new snow has been redistributed by winds blowing from a variety of directions.

The mid and lower snowpack are generally well settled, however an aging weak layer of surface hoar from late December, currently buried 70 to 150 cm deep, has shown surprisingly long-lived instability on slopes between 1700-2400 m (above the crust elevation and below the most wind-affected elevations), warranting increased caution around steeper slopes in this elevation band, particularly in the southern half of the region.

Terrain and Travel

Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Recent wind has varied in direction so watch for wind slabs on all aspects.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.