Avalanche Forecast

Archived

Dec 23rd, 2019–Dec 24th, 2019

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

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.

Regions

Kootenay Boundary.

Avalanche observations in the wake of the storm are extensive and artificial triggers continue to cause very large and destructive avalanches. These avalanches are releasing on a variety of weak snowpack layers. Conservative terrain selection remains absolutely essential.

Confidence

High -

Weather Forecast

Monday night: Cloudy with isolated flurries and a trace of new snow. Light southwest winds.

Tuesday: Cloudy with continuing isolated flurries and a trace of new snow. Light southwest winds. Alpine high temperatures around -7.

Wednesday: A mix of sun and cloud with cloud decreasing. Light northeast winds. Alpine high temperatures around -8.

Thursday: Mainly sunny with cloud increasing over the day. Light to moderate southwest winds. Alpine high temperatures around -7.

Avalanche Summary

A widespread avalanche cycle occurred on Saturday, with observations of large artificially triggered avalanches continuing into Sunday. Many of these recent avalanches released within the storm snow, and large avalanches have been observed on all aspects and generally above 2000 m. Numerous other large to very large avalanches have also been triggered by explosives on the late-November layer described in our Snowpack Summary.

Snowpack Summary

The past few stormy days have seen around 60 to 90 cm of snow deposited in the region, accompanied by strong west wind. This snow has loaded multiple weak layers, including:

a feathery surface hoar layer now buried around 60 to 100 cm.
an older surface hoar layer buried about 80 to 120 cm, associated with a melt-freeze crust on steep south aspects.
a complex layer of weak and sugary faceted snow, surface hoar, and melt-freeze crusts in the bottom half of the snowpack, buried in late November.

There is uncertainty on which of these layers will emerge as our primary persistent slab problem. However, given our extensive recent avalanche activity, it is prudent to expect that any one of these deeply buried layers could produce large and destructive avalanches with a human trigger.

Terrain and Travel

Don't let the desire for deep powder pull you into high consequence terrain.
Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Make conservative terrain choices and avoid overhead hazard.

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.