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Avalanche Forecast

Archived

Apr 14th, 2021–Apr 15th, 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.

Sustained warming continues to increase the likelihood for large cornice failures and wet loose avalanches. Start early and plan to be off large slopes before the heat of the day. 

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

Confidence

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

Weather Forecast

  

WEDNESDAY NIGHT: Clear / Light, southeast ridgetop wind / alpine low temperature 5 / Freezing level 2800 m.

THURSDAY: Sunny / Light, south ridgetop wind / alpine high temperature 10 / Freezing level 3000 m.

FRIDAY: Sunny / Light, south ridgetop wind / alpine high temperature 10 / Freezing level 3000 m.

SATURDAY: Sunny / Light, southwest ridgetop wind / alpine high temperature 9 / Freezing level 3000 m.

Avalanche Summary

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

On Tuesday, there were numerous wet loose avalanches on steep sun-exposed slopes up to size 2 as well as some size 2 wind slab avalanches in the alpine triggered by cornice falls. See 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

  • Extra caution is needed around cornices under the current conditions.
  • Avoid exposure to slopes that have cornices overhead.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Carefully evaluate steep lines for wind slabs.

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.