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Avalanche Forecast

Archived

Mar 4th, 2013–Mar 5th, 2013

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.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal.

Confidence

Fair

Weather Forecast

Synopsis: A ridge of high pressure will maintain mostly sunny skies for the next few days. The freezing level should rise to around 1000-1200 m during the day and drop back to valley bottom overnight. Ridgetop winds could be in the moderate to strong range from the east on Tuesday, but will ease off to light from the northwest for Wednesday and Thursday.

Avalanche Summary

Sunshine and warming have triggered loose avalanches and cornice failures over the last couple of days. An explosive triggered cornice in the Bear Pass area on Sunday did trigger a size 2.5 slab on the slope below. This slab failed within the latest storm snow and showed limited propagation.

Snowpack Summary

About 40-70 cm recent storm snow is showing signs of stabilizing. Recent strong, variable winds left wind slabs at treeline and alpine elevations. Direct sun is weakening the snowpack on sunny aspects during the day. A layer of surface hoar, facets and/or a crust is buried in the upper snowpack, but most operators report a good bond at this interface. Watch out for cornices, as they are large and fragile. Some large cornice falls have been reported over the past few days. Most have not triggered slabs on the slopes below, however at least one triggered a very large avalanche. The mid snowpack layers are generally well settled and strong. Facets at the base of the snowpack have resurfaced as a concern now that spring is on the doorstep and full-depth releases are becoming more likely.

Problems

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.

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.