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Avalanche Forecast

Archived

Apr 10th, 2021–Apr 11th, 2021

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

Regions

Northwest Coastal.

Recent snow and strong winds from shifting directions which have formed fresh wind slabs on a variety of aspects at treeline and above. Watch for newly formed and reactive wind slabs as you transition into wind affected terrain and avoid slopes with large cornices overhead.

Confidence

High -

Weather Forecast

  

SATURDAY NIGHT: Mostly cloudy with isolated flurries; 0-3 cm. / Strong, northwest ridgetop wind / alpine low temperature -10 / Freezing level valley bottom.

SUNDAY: Sunny / Moderate, northwest ridgetop wind / alpine high temperature -1 / Freezing level 800 m.

MONDAY: Sunny / Light, south ridgetop wind / alpine high temperature 5 / Freezing level 1500 m.

TUESDAY: Sunny / Moderate, west ridgetop wind / alpine high temperature 8 / Freezing level rapidly rising to 2500 m.

Avalanche Summary

Explosive and machine triggered storm slabs were reported up to size 2.5 in this region on Friday.

Large natural and explosive triggered glide slab avalanche activity has been ongoing for the past few weeks. Glide cracks releasing as full depth glide slab avalanches are extremely difficult to predict. Best practice is to avoid slopes with glide cracks.

Snowpack Summary

20-30 cm of recent snow has been accompanied by periods of strong winds from shifting directions which have formed fresh wind slabs on a variety of aspects at treeline and above. At lower elevations, the new snow is sitting on a melt-freeze crust.

Cornices are large, looming, and capable of triggering large avalanches when they fail. 

The mid/lower snowpack is well settled and strong in most areas.

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

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid lee and cross-loaded terrain.
  • Avoid exposure to slopes that have cornices overhead.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Problems

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.

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.

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.