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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

South Coast Inland.

Warm temperatures and sunshine will weaken cornices and the snowpack. Avoid exposure to sun exposed slopes and cornices, especially in the afternoon. 

Check out the latest Forecaster's Blog for more information on managing these conditions.

Confidence

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

Weather Forecast

A ridge of high pressure, with sunny skies and high freezing levels will dominate the weather pattern this week.

Tuesday night - Mainly clear / moderate northeast wind / alpine low temperature near -1 / freezing level 1500 m, possible alpine temperature inversion

Wednesday - Sunny / light to moderate northeast wind / alpine high temperature near 2 / freezing level 2700 m 

Thursday - Mainly sunny / moderate northeast wind / alpine high temperature near 3 / freezing level 3000 m 

Friday - Mainly sunny / light southeast wind / alpine high temperature near 5 / freezing level 3200 m

Avalanche Summary

There have been several size 1-2.5 natural and human triggered storm and wind slab avalanches reported over the past week. These were mainly on northerly aspects in the alpine and at treeline. There have also been several cornice failures, and small wet loose avalanches reported.

Looking forward, wet loose avalanches are expected with sun and warm temperatures. The likelihood of cornice failure also increases with warming. Wind slabs may still be possible to trigger at upper elevations.

Snowpack Summary

A storm late last week brought between 10-20 cm of new snow in the north, and 20-30 cm near the Coquihalla. The new snow fell on a crust in many areas.

The snow surface is now a crust in most areas, except on north aspects above about 1800 m, where both soft snow and wind slabs may exist. In areas where the surface is a crust, sunshine and rising freezing levels are expected to soften the crust during the day.

Cornices are large and looming along ridgelines. Their release is unpredictable but increases in likelihood with daytime warming, requiring a large berth if you're travelling above or below them.

Terrain and Travel

  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Avoid exposure to sunny slopes, especially in the afternoon.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Cornices become weak with daytime heating or solar exposure.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

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.