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Avalanche Forecast

Archived

Jan 19th, 2013–Jan 20th, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast.

Confidence

Good

Weather Forecast

The stationary ridge of high pressure is expected to bring continued dry conditions to the region for the forecast period. Alpine temperatures are forecast to be about 3.0` for Sunday and Monday, and then dropping on Tuesday. Winds should remain mainly light from the west.

Avalanche Summary

Recent observations mostly involve snowballing and several wet loose sluffs up to Size 2 on sun-exposed slopes. A few wind slabs were observed to size 2 in the north of the region. They were formed by strong west winds a few days ago and have most likely gained some strength.

Snowpack Summary

Above freezing temperatures at higher elevations have caused snow surfaces to moisten on sun-exposed slopes; however, a nightly crust recovery is likely with forecast clear skies. The surface snow on northerly aspects is dry and wind-pressed with continued surface hoar growth at lower elevations. Below this, 40-80 cm of settling storm snow sits on a persistent weakness of buried surface hoar, facetted snow, and /or a crust. Recent snowpack tests show that this interface is gaining strength but may still be susceptible to human triggering . No significant weaknesses have been reported recently below this in the mid snowpack layers. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by warming or heavy triggers in steep, shallow, rocky terrain where more facetting has taken place.

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.

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.