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Avalanche Forecast

Archived

Jan 31st, 2013–Feb 1st, 2013

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

Regions

Sea To Sky.

Confidence

Good

Weather Forecast

The offshore upper ridge will start to move onto the coast pushing the polar front to the North bringing rising freezing levels, and sunny skies. Friday: A mild SW flow will show no new precipitation and ridgetop winds will be light from the West. Alpine temperatures will rise to 3.0 degrees and freezing levels will rise to 2200 m. Expect periods of Alpine sun and solar radiation.Saturday: Continued warm temperatures and sunny skies providing a strong solar influence. Alpine temperatures will rise to 4.0 degrees and freezing levels will be near 2400 m. Ridgetop winds will be light from the SW.Sunday: Dominating ridge will start breaking down bringing light-moderate precipitation. Alpine temperatures will drop to -3.0 with freezing levels falling to 1300 m.

Avalanche Summary

Numerous natural slab avalanches size 1.0-2.5 on NE-E aspects, one being a cornice release, and others releasing on older buries surface hoar layers. Rider triggered size 1.0 on SE aspect at 1500 m on most recently buried surface hoar/crust interface. Numerous natural loose wet avalanches from  steeper solar aspects up to size 1.0. With forecast rising freezing levels and a high solar influence, loose wet avalanches will continue and potentially step down and entrain most snow above the buried surface hoar/crust interface.

Snowpack Summary

The upper snowpack is showing continued settlement and gaining strength, although forecast rising alpine temperatures and sunny skies will affect and weaken the upper snowpack.  Wind slabs are still found behind ridges, ribs and on lee slopes. Snow amounts (20-50 cm)  sits on a  variety of old surfaces including wind slabs, crusts and surface hoar crystals that are mainly found in sheltered locations (treeline and below, northerly aspects). This layer has been slightly touchy generally from isolated sheltered areas where the surface hoar had a chance to form. Down deeper sits another surface hoar layer (40-80 cm) which seems to be gaining strength with little to no recent reactivity on it. Below this sits a generally well settled mid pack, which may be bridging a basal facet/crust layer in deeper snowpack areas. The average snowpack depth at treeline is near 170 cm.

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.

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.

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.