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Avalanche Forecast

Archived

Feb 13th, 2018–Feb 14th, 2018

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

Regions

South Coast Inland.

Stay disciplined while avalanche danger is heightened. Wind slabs remain reactive to human triggering and will be building with new snow and wind over Tuesday night

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Tuesday: Flurries bringing around 4-8 cm of new snow. Moderate to strong west winds.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate north winds. Alpine high temperatures of -9 in the north of the region, closer to -3 in the south.Thursday: A mix of sun and cloud with cloud and light flurries building over the day. Light southwest winds. Alpine high temperatures of -12 in the north of the region, closer to -6 in the southFriday: A mix of sun and cloud with isolated flurries and a trace of new snow. Moderate northwest winds. Alpine high temperatures of -10 in the north of the region, closer to -3 in the south.

Avalanche Summary

Reports from Sunday included observations of numerous small wind slabs releasing with skier traffic and ski cutting on steep treeline and alpine features in the north of the region. This was after a bout of intense wind loading from strong to extreme northerly winds. One natural size 2.5 wind slab release was also observed on a southeast aspect.On Saturday, skiers triggered a size 2 wind slab on a north east aspect near 2000m in the Duffey zone. See the MIN report for more details. Friday there were isolated reports of natural cornice triggered and wind slab activity up to size 2.5, as well as evidence of an older large, natural size 3.5, in high alpine terrain in the Duffey Lake area.On Thursday, the southern part of the region reported a natural slab avalanche size 3.5 from a NE-SE aspect near 1800 m and numerous wet slabs up to size 2.5. An avalanche control mission using explosives in the northern part of the region saw wind slab results up to size 1.5, only running in the surface snow and not stepping down deeper.

Snowpack Summary

5-10 cm of new snow is expected to fall by Wednesday morning. The new snow is accumulating above unconsolidated recent storm snow in wind-sheltered, shaded areas at upper elevations as well as variably scoured and wind loaded slopes in exposed areas. The recent storm snow amounts to roughly 60 cm in the south of the region and about half this amount in the north of the region. Below about 1800 metres, the new snow will accumulate above a rain crust.About 80-150 cm down in the mid snowpack sits the mid-January crust. It generally shows signs of bonding to the overlying snow but will likely remain sensitive to large triggers - especially in thinner snowpack areas. Large, looming cornices exist, they are fragile, and they demand respect. Cornice falls are very effective triggers for avalanches on the slopes below them.

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.