Avalanche Forecast

Archived

Feb 25th, 2020–Feb 26th, 2020

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast Inland.

Avalanche danger will be a step higher in the south half of the region where storm slabs are deeper, more wind-affected and may sit over a weak layer.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

Tuesday night: Scattered flurries bringing a few cm of new snow. Southwest wind light in the north, moderate to strong in the south. Freezing level 1000 m.

Wednesday: Isolated flurries. Light southwest wind. Freezing level 1300 m.

Thursday: Mix of sun and cloud. Light to moderate southwest wind. Freezing level 1500 m.

Friday: Mix of sun and cloud. Light to moderate southwest wind. Freezing level 1600 m in the north, 2000 m in the south.

Avalanche Summary

Natural wind slab avalanches were observed on northeast to west aspects in the alpine size 1.5-2, as well as skier controlled size 1-1.5 out of wind loaded pockets. Reports of avalanche activity over the weekend were limited to loose dry and soft slab avalanches to size 1.5 in the north of the region

Snowpack Summary

15-30 cm of recent snow, and as high as 50 cm in the Coquihalla, may overly isolated patches of surface hoar in sheltered areas at low elevations or sun crusts on solar aspects. In parts of the region that did not receive wind, the snow remains low density and evenly distributed all except exposed ridgetops. In windier areas, deep wind loaded pockets have been observed in lee features in the alpine.

In the north part of the region (e.g. Duffey/Hurley/Goldbridge), a deep instability exists in the snowpack, consisting of a weak basal facet-crust complex. Sporadic avalanche activity on this layer is keeping it on our radar, with the latest report described here. In the south of the region, including the Coquihalla and Manning areas, there are no concerns about deeply buried weak layers.

Terrain and Travel

Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
Surface hoar distribution is highly variable. Avoid generalizing your observations.
If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.