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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

Sea To Sky.

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

Loose wet avalanches to size 1 have been reported in steep, sun-exposed terrain.

Snowpack Summary

Above freezing temperatures 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-affected with continued surface hoar growth at lower elevations. 40-80 cm below the surface is a persistent weakness of surface hoar that was buried at the beginning of January. Recent tests have shown moderate results at this interface with resistent planar fracture characteristics. Although not widespread, this layer seems to be found in portions of sheltered terrain near treeline, and may still be fairly well preserved. 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 unsupported, 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.