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Avalanche Forecast

Archived

Mar 31st, 2021–Apr 1st, 2021

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

Regions

North Columbia.

Flurries and increasing winds should sustain wind slab problems at high elevations while light rain maintains some potential for wet loose activity lower down. Stay aware of cornices that formed fragile new growth during the storm. 

Confidence

Moderate -

Weather Forecast

Wednesday night: Clearing, becoming cloudy again by morning. Moderate to strong southwest winds, increasing into the morning. Freezing level remaining near 1500 metres.

Thursday: Cloudy with flurries bringing up to 5 cm of new snow, continuing but easing overnight. Moderate to strong southwest winds, easing by evening. Alpine high temperatures around -4 with freezing levels to 1600 metres.

Friday: Cloudy with continuing scattered flurries with up to 5 cm of new snow, continuing overnight. Light southwest winds. Alpine high temperatures around -5 with freezing levels to 1600 metres.

Saturday: Cloudy with continuing scattered flurries and up to 5 cm of new snow. Light to moderate southwest winds. Alpine high temperatures around -2 with freezing levels to 1800 metres.

Avalanche Summary

A natural storm slab avalanche cycle was observed to have run during the storm, widespread size 3-3.5 in the Selkirks and to a more limited extent in the Monashees to size 2, a few of them cornice-triggered. Storm slabs remained reactive to ski cuts on Monday, mostly around size 1 with a couple of skier remotes size 1-2 in the east of the region. By Tuesday, storm slabs were showing signs of becoming more stubborn, showing limited propagation with a few explosive control results around size 2. A skier triggered size 2.5 involvement in neighboring Glacier National Park resulted in lost gear and minor injuries.

Snowpack Summary

Thin new surface crusts have likely formed on solar aspects and below about 2000 metres. Forecast precipitation will likely keep surfaces wet at lower elevations while adding light amounts of dry snow to surfaces above 1500 metres. 

20-50 cm of recent snow in the Selkirk mountains and 5-10 cm elsewhere has otherwise seen some redistribution by southwest to northwest wind, and seems to be bonding well with underlying surfaces.

At alpine and treeline elevations, a widespread crust exists (except on north-facing slopes above 1800 m) buried 50-100 cm deep. Overall the snow seems to be bonding well at this interface, although there have been a few isolated avalanches running on deeper crust layers over the past few weeks.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Extra caution is needed around cornices under the current conditions.
  • Be alert to conditions that change with elevation.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.