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Avalanche Forecast

Archived

Mar 28th, 2013–Mar 29th, 2013

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

Regions

Northwest Inland.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

No precipitation is expected for the forecast period. Mainly clear skies are forecast for Friday and Sunday, although high cloud is expected on Saturday.Winds will be light from the west on Friday switching to light and northwesterly on Saturday and Sunday.Freezing levels will climb steadily from 1200m on Friday to about 2200m on Sunday.

Avalanche Summary

Numerous loose wet avalanches have occurred from steeper solar aspects up to size 2.0. Size 2 cornice releases have also been noted. There was also a report of a size 2 slab avalanche which involved sun-exposed recent storm snow which reacted on a buried sun crust.

Snowpack Summary

Many parts of the region have experienced strong winds that redistributed surface snow on lee aspects creating stiff wind slabs. At lower elevations and on sun-exposed slopes, snow surfaces are well into a melt-freeze cycle.30 - 60 cm of snow overlies a crust, old wind slabs or surface hoar layer buried on March 9th. Currently, this layer seems to be less reactive, but may still be a concern in some areas (low probability-high consequence). Recent snowpack tests are showing hard, resistent shears. This layer may be healing in some places, but I would remain conservative and continue to dig and test before diving into my line. The distribution of the surface hoar is variable and it may not exist, or be reactive, in every drainage. Deeper in the snowpack, basal facets may resurface as a concern with further warming.Cornices have become well-developed and could easily become unstable during periods of warm weather or direct solar radiation. Most snow surfaces exist on solar aspects up to 2300 m, forming a melt-freeze crust overnight.

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.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.