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Avalanche Forecast

Archived

Jan 14th, 2013–Jan 15th, 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 unlikely, human triggered possible.
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 unlikely, human triggered possible.

Regions

Northwest Coastal.

Confidence

Fair

Weather Forecast

Tuesday: Mainly cloudy with a chance of flurries and/or freezing drizzle. An above freezing layer (AFL) is likely between 1000 and 2000 m. Winds are strong from the west.Wednesday: Light snow – 5-10 cm. The freezing level returns to 600-800 m. Winds to strong from the west. Thursday: Light to moderate snow – 10 cm. The freezing level is around 1000 m. Winds are strong from the southwest.

Avalanche Summary

On Sunday there was a report of a size 1.5 skier triggered avalanche on a steep unsupported convex roll on a northerly aspect. This event likely released on the late December surface hoar layer approximately 60 cm deep. There are also a few reports of glide releases in steep south facing terrain.

Snowpack Summary

The snow surface has probably changed from facetted snow and/or surface hoar to a dusting of new snow, a rain or freezing rain crust, and new dense wind slabs depending on aspect and elevation. Below this 60-90 cm of storm snow from last week continues to settle and gain strength. However, a weak layer of surface hoar or facetted snow sits at the base of the storm snow and continues to react in snowpack tests and slope tests. Near the base of the snowpack, a crust/facet layer continues to concern local avalanche professionals. This seems most prevalent near Bear Pass where the snowpack distribution is quite variable. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

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.

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.