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Avalanche Forecast

Archived

Apr 6th, 2012–Apr 7th, 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, 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

Northwest Inland.

Confidence

Good

Weather Forecast

A ridge off high pressure off the coast will bring sunny, dry conditions through the weekend. Saturday: Ridgetop winds will be light from the SE. Alpine temperatures near -1. Freezing levels rising to 1400 m, dropping to valley bottom through the night. Sunday/Monday: Clear, sunny and dry conditions. Freezing levels rising to 1700 m both days. The ridge will start to break down on Monday bringing bands of cloud, and light precipitation through the evening. Solar radiation will be intense through the forecast period.

Avalanche Summary

Reports from Wednesday include some larger wet sluffs from steep rocky sun-exposed terrain. Cornices have also been failing over the past couple of days, some of which triggered wind slab avalanches up to Size 2 on the slope below. Glide cracks are widening at lower elevations.

Snowpack Summary

Moderate winds have blown light amounts of new snow into variable wind slabs in exposed lee and cross-loaded terrain, which are starting to bond. Surface snow on sun-exposed slopes is undergoing a daily melt-freeze cycle. In sheltered areas 15-30cm of new snow sits on the previous surface that includes crusts (found on all aspects below 1000m and on solar aspects higher up), and old wind slabs. Not only will daytime warming and sun-exposure cause surface snow to lose cohesion and cornices to weaken, they will also increase settlement rates and decrease slab stability.

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.

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.