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Avalanche Forecast

Archived

Jan 16th, 2013–Jan 17th, 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.

Regions

Sea To Sky.

Confidence

Good

Weather Forecast

Synopsis: The upper ridge of high pressure continues to dominate the weather for the South Coast. The next few days should see mainly clear skies with possible valley cloud. The above freezing layer between 1000 and 3000 m should remain. Winds are generally moderate to strong from the northwest.

Avalanche Summary

On Wednesday there were reports of a few small loose wet avalanches on steep sun exposed slopes, and couple accidentally skier-triggered size 1 slab or loose snow avalanches in steep south facing terrain.

Snowpack Summary

The snow surface consists of thin new wind slabs, a sun crust, moist snow, dry faceted snow, or large surface hoar depending on aspect, elevation, and time of day. Below this 40-70 cm of  recent storm snow sits on a persistent weakness of surface hoar, facetted snow, and/or a crust buried at the beginning of January. Reports from last weekend include a Rutschblock Score of 3 down 52cm on a thin crust in the Whistler area, and hard compression test results on distinct surface hoar on a northeast facing open glade below treeline in the Chehalis (northwest of Hope). 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 heavy triggers in steep, shallow, rocky terrain where more facetting has taken place.

Problems

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.

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.