Avalanche Forecast

Archived

Dec 17th, 2022–Dec 18th, 2022

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

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.

Danger ratings have decreased but concern still remains for deeper weak layers and lingering wind loaded features.

A deep persistent slab problem is present, which is uncommon for this region. Good travel habits and conservative terrain choices are tools to manage this problem.

Confidence

Moderate

Avalanche Summary

As northerly winds are expected to continue to redistribute snow, rider triggered wind slabs remain possible.

On Monday near Pemberton, a skier-triggered persistent slab avalanche occurred on a northwest aspect in the alpine, on a crust and surface hoar layer. This avalanche triggered a size 2 on a nearby slope, on facets and depth hoar near the ground level. Settlements (a sign of instability) have been reported in shallow and rocky features where weak layers sit shallower and closer to the surface.

If you head out into the mountains, please share your photos or observations on the Mountain Information Network. Your information helps us understand local conditions!

Snowpack Summary

In exposed terrain at higher elevations, pockets of wind slab sit in wind loaded features. Strong winds have pushed this snow into features lower on slopes than typically seen. Large surface hoar has been reported on the surface in sheltered areas, with a crust present on solar aspects.

Two weak layers of concern sit in the snowpack:

A layer of surface hoar from early December is buried 20-40 cm deep. This layer can be found in sheltered and shaded terrain features.
The mid and lower snowpack consist of crusts and facet layers, with depth hoar observed near the ground, which is very weak and highly uncommon for this region.

The snowpack is currently weak and shallow for mid December. In deeper areas, snowpack depths only reach 100-130 cm.

Weather Summary

An Arctic front dominates the weather over BC. Light snowfall is expected Saturday night as a low south of Vancouver Island briefly competes with the cold air.

Saturday Night

Mostly cloudy with 5 cm of snow possible. Moderate southwesterly winds continue. Freezing level below valley bottom.

Sunday

A mostly cloudy with a trace to 3 cm of snow possible. Moderate westerly winds continue at ridgetop. Temperatures drop further, with alpine highs of -22°C.

Monday

Clearing skies with moderate to strong westerly winds. Freezing level below valley bottom. Alpine high of -24 °C.

Tuesday

Cloudy skies with moderate to strong westerly winds. Light snowfall. Freezing level below valley bottom, alpine high of -20 °C.

Monday

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid freshly wind loaded terrain features.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Conditions 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.

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.