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Avalanche Forecast

Archived

Dec 12th, 2015–Dec 13th, 2015

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

Regions

Northwest Coastal.

Conditions below treeline vary greatly. Many areas are still below the threshold for avalanches, but buried surface hoar may be present as you gain elevation.

Confidence

Moderate

Weather Forecast

On Sunday, expect mainly cloudy skies and light northwest winds. By late Monday and Tuesday, the region could see up to 15cm of new snow and strong southwest winds. The freezing level should hover around valley bottom for the entire forecast period.

Avalanche Summary

In recent days, explosives avalanche control in the north of the region produced a few wind slab avalanches to size 2. No other avalanches have been reported.

Snowpack Summary

Up to a meter of settled snow may be sitting upon a weak layer of buried surface hoar. In some areas, this layer may be primed for human triggering and wide propagations while in other areas it is non-existent or has gained significant strength. Due to the variable nature of this weak layer, I'd dig down to test for it before committing to any steep lines. I'd also be increasingly cautious on sheltered slopes at or below treeline.Strong north through easterly winds have been responsible for a recent reverse-loading pattern, and wind slabs may still be sensitive to human triggering on lee features. Low-elevation slopes below treeline may still be bellow threshold for avalanches in many places.

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.