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Avalanche Forecast

Archived

Apr 7th, 2022–Apr 8th, 2022

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

Regions

Northwest Coastal.

In the south of the region, another 15-30 cm snow will fall by the end of the day Friday and continue to build reactive storm slabs. Moderate to strong south and west wind will form fresh wind slabs in lee terrain features in the alpine and at treeline. 

Confidence

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

Weather Forecast

Thursday night: Cloudy, 15-25 cm snow in the southern half of the region, moderate to strong south wind, alpine low -2 °C, freezing level at 1000 m.

Friday: Mix of sun and cloud, 5-10 cm snow, moderate to strong west wind, alpine high -3 °C, freezing level at 1000 m.

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

Sunday: Sunny, trace of new snow, light to moderate northeast wind, alpine high -3 °C, freezing level at 1000 m.

Avalanche Summary

A few large wind slabs up to size 3 as well as several storm slabs to size 2 were triggered with explosives on Wednesday. Several small natural dry loose avalanches were reported, as well as a large (size 2.5) cornice failure. Skiers triggered several small wind slab avalanches in the alpine. 

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.

Snowpack Summary

20-40 cm new snow add to 30-60 cm recent snow, which overlies a hard melt-freeze crust. The previous snow surface was wind affected and in some wind-exposed areas the wind had scoured the snow down to the crust. 

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.
  • Even brief periods of direct sun could produce natural avalanches.

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.