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Avalanche Forecast

Archived

Feb 10th, 2013–Feb 11th, 2013

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

Regions

Cariboos.

Confidence

Fair - Timing of incoming weather is uncertain on Tuesday

Weather Forecast

Monday: The pattern and flow starts changing today as the ridge move southward and a zonal flow sets up. An embedded cold front will move through the region bringing moderate NW winds and a trace of snow. Treeline temperatures will sit near -3 and freezing levels will be around 1100 m. Tuesday: The fast paced zonal flow will continue with a trough moving in from the West bringing moderate-strong SW winds and light-moderate snow accumulations. Treeline temperatures will be near -5 and freezing levels around 900 m.Wednesday: Another ridge is building bringing dryer conditions; especially for the short term. Ridgetop winds will be light from the West. Treeline temperatures -10 and freezing levels near 500 m falling to valley bottom overnight.  

Avalanche Summary

On Saturday, a natural slab avalanche size 1.5 and several loose dry avalanches from steep terrain features were reported.

Snowpack Summary

Up to 40 cm of new snow is sitting on old wind slabs and recently buried weak layers. Old storm snow has settled into a dense slab that sits on a persistent weak interface deeper (40-80 cm down) in the snowpack. Buried crusts, surface hoar and facets are acting as those weak interfaces. Use extra caution on large open slopes, cutblocks and convex rolls at and below treeline where buried surface hoar may be preserved.Wind slabs continue to develop and stiffen on lee slopes and behind terrain features like ridgelines and ribs. Reverse loading may occur with changing winds. Unsuspecting slopes may catch you by surprise. The mid-pack is generally well settled and strong and the average snowpack depth at treeline elevations is near 200 cm. Cornices have grown and could threaten the slopes below.

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.