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Avalanche Forecast

Archived

Apr 12th, 2021–Apr 13th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Northwest Coastal.

Danger will elevate throughout the day as slopes warm up. Plan your day around avoiding cornices and sun-exposed slopes. Read more in this Forecasters' Blog.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

MONDAY NIGHT: Partly cloudy skies, 20 km/h southwest wind, freezing level steady around 1300 m with treeline temperatures around 0 C.

TUESDAY: Mix of sun and cloud, 20 km/h southwest wind, freezing level climbs from 1300 to 1700 m throughout the day, treeline temperatures climb to +4 C.

WEDNESDAY: Sunny, light southwest wind, freezing level climbs from 2000 to 2700 m throughout the day, treeline temperatures climb to +8 C.

THURSDAY: Sunny, light southwest wind, freezing level steady around 2800 m, treeline temperatures around +8 C.

Avalanche Summary

Warm sunny weather this week will likely cause wet loose avalanches on sun-exposed slopes and large cornice falls.

Over the weekend there were a few reports of size 2 human triggered slab avalanches around Shames and Kitimat. There were also numerous reports of large cornice failures (size 2-2.5), some of which triggered wind slab avalanches on the slopes below. Additionally, small (size 1) wet loose avalanches on solar aspects were reported at all elevations.

Snowpack Summary

Sunny skies and rising freezing levels will result in melting surfaces on solar aspects and lower elevations. 20-30 cm of recent snow is quickly settling and strengthening, although wind slabs could linger at upper elevations. The mid/lower snowpack is well settled and strong in most areas. Cornices are large and looming along ridgelines, and are capable of triggering avalanches when they fail.

Glide cracks releasing as full depth glide slab avalanches become more common in the spring and are extremely difficult to predict. Best practice is to avoid slopes with glide cracks.

Terrain and Travel

  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • Avoid exposure to slopes that have cornices overhead.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.

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.