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Avalanche Forecast

Archived

Jan 20th, 2020–Jan 21st, 2020

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.

Pockets of wind slab may be encountered at upper elevations. Use caution around wind loaded features.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

MONDAY NIGHT - Mainly cloudy with isolated flurries / south wind, 10-30 km/h / alpine low temperature near -3

TUESDAY - Flurries, 5-10 cm / south wind, 10-30 km/h / alpine high temperature near -2

WEDNESDAY - Cloudy with isolated flurries / southwest wind, 15-25 km/h / alpine high temperature near -4

THURSDAY - Flurries, 5-10 cm / southwest wind, 30-50 km/h / alpine high temperature near 0 / freezing level 1800 m

Avalanche Summary

Avalanche activity was pretty quiet on Sunday and Monday with one report of an explosives triggered size 2.5 loose snow avalanche.

On Thursday and Friday there were reports of numerous natural, human and explosives triggered size 1-2.5 storm and wind slab avalanches.

No new persistent slab avalanches were observed in the past few days, but this region has been highlighted for recent persistent slab avalanche activity. A number of natural and explosives triggered persistent slab avalanches up to size 3 were reported just over a week ago.

Snowpack Summary

Stormy weather over the past several days brought 35 to 65 cm of snow to the region with moderate to strong winds from a variety of directions. This, combined with recent warm temperatures, will have likely formed fresh storm slabs in many areas.

There are two weak layers of surface hoar found around 70 to 130 cm deep. These layers are especially concerning in steep, sheltered, large terrain features and shallow rocky areas.

The base of the snowpack is also weak in parts of the region where it consists of sugary faceted snow around a melt-freeze crust.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Avoid freshly wind loaded terrain features.

Problems

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.

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.