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Avalanche Forecast

Archived

Dec 17th, 2019–Dec 18th, 2019

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, human triggered possible.

Regions

Kootenay Boundary.

Two persistent weak layers are at play in the region, with snowpack tests showing either one could react to a human trigger. Avoid overthinking the snowpack and instead focus on diligent travel practices and conservative terrain selection.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Cloudy with isolated flurries and a trace to 5 cm of new snow. Moderate southwest winds.

WEDNESDAY: Mainly cloudy. Light to moderate southwest winds. Alpine high temperatures around -6.

THURSDAY: Cloudy with isolated flurries and a trace of new snow, increasing overnight. Light to moderate southwest winds. Alpine high temperatures around -5.

FRIDAY: Cloudy with continuing snowfall bringing approximately 20 cm of new snow, with new snow totals of 30-40 cm. Precipitation transitioning to rain as high as 1400 metres as temperatures warm over the day to reach around -1 in the alpine. Freezing level rising to about 1600 metres.

Avalanche Summary

Observations from Monday showed only one small new skier-triggered wind slab at 1950 metres in Ymir bowl.

There were reports of a size 1 human triggered avalanche, and natural size 2 avalanche on Saturday that released on the persistent weak layer that is down about 50-60 cm.

Snowpack Summary

Light new snow amounts have buried a thin new layer of surface hoar likely to be found in more sheltered areas.

Including the new snow, collectively 25-35 cm of recent snow sits on another weak layer of surface hoar in many sheltered areas, and on a crust on steep south facing slopes. This layer may be more reactive to human triggers where wind loading has formed a deeper, stiffer slab above it.

Another persistent weak layer found approximately 60-100 cm deep consists of a tightly-spaced series of crusts with sugary faceted snow as well as suface hoar found in between them. This complex layer is more likely to be reactive to human triggers in shallow, rocky areas.

Problems

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.