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Avalanche Forecast

Archived

Apr 13th, 2021–Apr 14th, 2021

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.
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 sun-exposed slopes and cornices. Read more in this Forecasters' Blog.

Confidence

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

Weather Forecast

A high pressure ridge brings clear skies and progressively warmer temperatures.

TUESDAY NIGHT: Clearing skies, light southwest wind, freezing level climbs from 1700 to 2000 m by the morning with treeline temperatures climbing to +2 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 south wind, freezing level steady around 2800 m, treeline temperatures around +8 C.

FRIDAY: Mostly sunny, light south wind, freezing level steady around 2800 m, treeline temperatures around +8 C.

Avalanche Summary

Warm sunny weather this week will cause wet loose avalanches and cornice falls.

On Monday there were numerous wet loose avalanches on steep sun-exposed slopes (to size 2) as well as some natural wind slab avalanches in the alpine triggered by cornice falls. Over the weekend there were numerous size 1-2 human triggered storm and wind slab avalanches at treeline and alpine elevations around Shames and Kitimat (see photos in this MIN report). 

Snowpack Summary

Sunny skies and rising freezing levels will result in melting surfaces everywhere except north-facing alpine terrain. In the alpine 20-30 cm of recent snow is quickly settling and strengthening, although wind slabs may linger on some steeper slopes. The mid/lower snowpack is strong and settled in most areas. 

Cornices are large and looming along ridgelines, and are capable of triggering avalanches when they fail. Also, 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 minimize exposure to cornices and avoid slopes with glide cracks.

Terrain and Travel

  • Avoid exposure to sunny slopes, especially in the afternoon.
  • 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.