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Avalanche Forecast

Archived

Feb 19th, 2013–Feb 20th, 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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Cariboos.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Wednesday: Mix of sun and cloud / Light southwest winds / Freezing level at 700mThursday: Light snowfall intensifying in the evening / Moderate southwest winds / Freezing level at 900mFriday: Heavy snowfall / Moderate south winds / Freezing level at 800m

Avalanche Summary

Natural wind slab avalanches up to size 2.5  were reported from north to west aspects at treeline and above in the Blue River North area. As well, a size 2.5 natural slab avalanche released on a south face at 2400m. It is thought to have released on the February 12th interface.

Snowpack Summary

Variable amounts of new snow continue to add to the recent storm slab which sits above the February 12th weak surface hoar layer and a sun crust on solar aspects. This layer is now buried down about 30-70 cms depending on where you are in the region. New wind slabs developed at treeline and above due to the new snow and wind during the storm. These soft new wind slabs (hard slabs in some areas) are reported to be reactive and may be hiding stiffer wind slabs that are a couple of days older. Deeper persistent weak layers from early February and late January continue to show planar failures when moderate to hard forces are applied to snow profile tests. These deeper layers have not been reactive to the loads associated with recreationalists, but they may be triggered by large loads like an avalanche in motion, or a cornice fall.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.