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Avalanche Forecast

Archived

Feb 11th, 2012–Feb 12th, 2012

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

Regions

Northwest Coastal.

Confidence

Good - -1

Weather Forecast

Saturday night: light precipitation with 5-10 mm expected. Freezing level around 700 m. Strong southwesterly winds. Sunday: Winds veering to moderate northwesterly. Lingering flurries in the morning, later becoming dry as a high pressure ridge builds. Freezing level around 700 m. Monday: Dry and sunny. Light winds. Freezing level at valley bottom. Tuesday: another weak frontal system will bring light precipitation and moderate southwesterly winds.

Avalanche Summary

No recent avalanches have been reported from this region.

Snowpack Summary

Approximately 5 cm of new snow at treeline and above has buried a surface hoar layer (crystal size reported to be 1-4 mm) lying on old surfaces comprising crusts and variable wind slabs. The crusts formed in response to successive melt-freeze cycles and are harder and thicker the lower in elevation you go. The wind slabs were deposited on a variety of aspects and are becoming increasingly stubborn and difficult to trigger. Deeper within the snowpack, a facet layer buried around Jan 20th is the greatest concern. This layer lies approximately 110-140 cm below the surface and still exhibits hard, sudden planar results in isolated snowpack tests.

Problems

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.