Avalanche Forecast

Archived

Dec 8th, 2019–Dec 9th, 2019

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 possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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, human triggered possible.

Regions

South Columbia.

There is uncertainty with the reactivity of several buried weak layers. Best to adopt a conservative approach while the snowpack adjusts to the increased load from recent snowfalls.

Confidence

Moderate - Uncertainty is due to the complexity of the snowpack’s structure.

Weather Forecast

Sunday: Mainly clear with cloudy periods, alpine temperature -9, moderate northwest wind.

Monday: Mix of sun and clouds, alpine temperature -7, moderate north wind.

Tuesday: Mix of sun and cloud, alpine temperature -8, light northwest wind.

Wednesday: Cloudy with flurries, alpine temperature -8, light southwest wind.

Avalanche Summary

Reports from Friday indicate skier triggered and natural storm slab avalanches to size 1-2. Additionally there were explosives controlled avalanches to size 3 along the Trans Canada highway corridor on Friday. There were also a few reports of persistent slab avalanches failing on a layer of surface hoar (down 60-100 cm) at treeline elevations.

Snowpack Summary

20-40 cm of new snow from the latter part of last week has covered a layer of feathery surface hoar that has been found at all elevations in some parts of he region. A thick layer of faceted crystals, previously wind-affected surfaces, and/or surface hoar in sheltered areas (around treeline and below) is now 40-80 cm below the surface.

An additional layer of surface hoar may be found in sheltered areas around treeline down 60-100 cm. In some areas this may sitting on a thin crust.

A variety of crusts from late October are buried deeper in the snowpack.

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.

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.