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Avalanche Forecast

Archived

Apr 6th, 2022–Apr 7th, 2022

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

Regions

Northwest Coastal.

The south of the region is expecting up to 40 cm snow by the end of the day Thursday, combined with strong southwest wind. Storm and wind slabs will be reactive to human triggers.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

Weather Forecast

Wednesday night: Cloudy, 10-20 cm snow, most snow will fall in the south of the region, strong southwest wind, alpine low -4 °C, freezing level around 700 m. 

Thursday: Cloudy, 15-25 cm snow, most snow will fall in the south of the region, strong southwest wind, alpine high -2 °C, freezing level at 1100 m.

Friday: Mix of sun and cloud, 10-20 cm snow in the south of the region, moderate west wind, alpine high -3 °C, freezing level at 1000 m.

Saturday: Mix of sun and cloud, up to 5 cm snow, moderate west wind, alpine high -6 °C, freezing level at 700 m.

Avalanche Summary

Many small dry loose avalanches were reported on Tuesday. A cornice failed naturally and entrained snow on the slope below, resulting in a size 2.5 avalanche.

Intense wind loading triggered some very large (up to size 3.5) wind slabs in the Bear Pass area that were reported on Monday morning.

A size 1 storm slab 40 cm deep was skier triggered on a steep roll at treeline on Monday. Warming was reported as the contributing factor that made the slab more sensitive to triggering.

Snowpack Summary

The new snow will add to 30-60 cm recent snow which overlies a hard melt-freeze crust.

Recent moderate to strong winds from varied directions exposed the crust in some areas and formed wind slabs on a variety of aspects.

Around 100 cm down, a layer of weak snow (facets or surface hoar) has been occasionally reported in sheltered areas. The distribution of this layer has been reported as isolated and is likely not a problem in many areas.

Cornices are very large and exposure to them should be minimized, especially during warm or windy weather.

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.