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Avalanche Forecast

Archived

Apr 7th, 2022–Apr 8th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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

Purcells.

Continually assess the snow surface and watch for natural avalanche activity as you move through terrain. There is uncertainty in how the snowpack will respond to the rapidly changing freezing levels.

Confidence

Low - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Thursday night: No new snow expected. Moderate southwest winds shifting to strong south. Possibility of a temperature inversion with above freezing layer at treeline. 

Friday: Mostly cloudy with rain at lower elevations and up to 5 cm of new snow at higher elevations. Strong south winds. Freezing level around 2000 m in the north and near 3000 m in the south of the range.

Saturday: Mostly cloudy with light flurries bringing trace amounts of new snow. Light southwest winds and freezing levels around 1530 m.

Sunday: A mix of sun and cloud with no new snow expected. Light west winds and freezing levels around 1300 m.

Avalanche Summary

On Wednesday one size three natural wind slab was observed on a northeast aspect at 2300 m.

Over the past few days ski cutting has produced wind slab avalanches up to size 1.5. These avalanches have generally been on north and east aspects in treeline terrain. Explosive control has produced storm and wind slab avalanches up to size 2.5 on all aspects at treeline and above in the western part of the region where more storm snow was recorded. Several small cornice falls have also been observed .

We suspect that large wet loose avalanches will be observed with elevated freezing levels.

Snowpack Summary

Wind slabs could still be found in alpine terrain on north and east aspects. Moist snow will likely be observed on all aspects and elevations. A new crust will form as the freezing level falls in the evening. 

A thick rain crust with facets above from early December is buried around 150 cm deep. Large avalanches were naturally triggered on this layer during the last significant warming event in western terrain near the Bugaboos. Avalanche activity on this layer will become unlikely as the freezing level falls.

Terrain and Travel

  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Avoid exposure to slopes that have cornices overhead.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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.

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.

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.