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Avalanche Forecast

Archived

Dec 24th, 2018–Dec 25th, 2018

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
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.

Regions

Kootenay Boundary.

A weak layer lingers in our snowpack. It is a good time to remain conservative with your terrain selection. See this forecaster's blog, which describes this persistent problem: www.avalanche.ca/blogs/persistent-slab

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Mostly cloudy with some clear breaks, light west wind, treeline temperature -7,  freezing level in the valley bottom.TUESDAY: Mix of sun and cloud, light south wind, treeline temperature -6 C, freezing level 600 m.WEDNESDAY: Cloudy with scattered flurries, light southwest winds, treeline temperature -6 C, freezing level 500 m.THURSDAY: Mix of sun and cloud, light west winds, treeline temperature -7 C, freezing level 400 m.

Avalanche Summary

A few small (size 1) wind slab avalanches were observed at high elevations on Saturday. Large (size 2 to 3) slab avalanches were triggered by explosives on Friday. The avalanches were generally 10 to 40 cm deep and within recent storm snow.

Snowpack Summary

Strong winds have redistributed the recent storm snow, producing wind slabs in lee terrain features. These slabs likely won't bond well to underlying surfaces.Beneath this, around 50 to 100 cm of snow is poorly bonded to a rain crust and a weak layer of feathery surface hoar and sugary facets. Avalanche activity, remote triggering, and snowpack test results tell us that it is a critical layer. It is best to remain conservative and travel cautiously with this layer in the snowpack.The lower snowpack is well-settled.

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.

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.