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Avalanche Forecast

Archived

Nov 27th, 2021–Nov 28th, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Danger increases with heavy rain and high winds today. Minimize your exposure to avalanche terrain and overhead hazard as the snowpack becomes saturated and unstable.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

SATURDAY NIGHT: Another front brings windy and wet weather to the region in the evening. 10-25mm is expected overnight. Snow will become mixed precipitation and rain as freezing levels rise throughout the night, spiking above 2500m by early Sunday morning. Winds increase to extreme southwest winds as the storm progresses.

SUNDAY: Up to 10mm throughout the day with freezing levels remaining above 2000m. Strong southwest winds persist.

MONDAY: Winds shift to moderate westerlies with light accumulations as the storm exits.

TUESDAY: Yet another atmospheric river (moisture heavy weather system) hits the coast and begins to affect the interior. Moderate accumulations, strong winds and high freezing levels return. 

Avalanche Summary

On Friday November 26, a size 1.5 skier accidental storm slab was reported on the Mountain Information Network near Nelson. They noted a fast moving avalanche with wide propagation, supported by a hard bed surface.

On Wednesday, November 24th, multiple size 2.5 wind slabs were triggered by explosives in the Okanagan. These were reported on wind loaded east and southeast aspects up to 60cm deep.

Note that there are very few field observations in the Kootenay Boundary this early in the season. Backcountry users need skills in assessing conditions and decision making. 

Snowpack Summary

25mm of mixed precipitation and rain will fall on recent settling storm snow. In the Okanagan a 2mm rain crust may sit between the new and old storm snow. 

The mid-November crust is down 25-50 cm and is up to 10 cm thick. The lower snowpack is a series of crust and facet layers. At the bottom of the snowpack, up to 20 cm of faceted snow may be found. Snowpack depths at treeline range from 40-100 cm, with alpine depths exceeding 150 cm in areas. Below 1700m, snowpack depths decrease rapidly.

Terrain and Travel

  • Be alert to conditions that change throughout the day.
  • Avoid avalanche terrain during periods of heavy rain.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.