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Avalanche Forecast

Archived

Feb 22nd, 2014–Feb 23rd, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Coast.

Conditions are primed for triggering avalanches. Conservative decision making is essential. Check out the latest forecaster blog for more discussion on the current conditions.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Synopsis: One more warm front should pass across the South Coast late Sunday spreading light to moderate snowfall through Monday morning. A ridge of high pressure builds in on Monday kicking off a drying trend. Sunday: Flurries or light snow – 5-10 cm. The snow line is near sea level. Ridge winds are moderate from the W-NW. Monday: Flurries ending early, followed by a mix of sun and cloud. The freezing level is around 500 m. Winds are moderate from the north, easing to light. Tuesday: A mix of sun and cloud. The freezing level is around 1000 m. Winds are light.

Avalanche Summary

A number of very large (size 3-4) natural and explosive triggered slab avalanches occurred near the Coquihalla Pass on Friday. These events were in response to rapid loading from new snowfall and strong winds and showed impressive propagation. In other areas natural activity was limited to relatively small moist loose snow avalanche from solar aspects. Whumpfing and cracking continue to be reported and the potential for triggering the mid-February persistent weakness remains high.

Snowpack Summary

In the last week, the northern part of the region received over 1 m of new snowfall, while southern areas saw almost 2.5 m (and counting). Strong winds have created dense wind slabs on exposed lee slopes and in cross-loaded terrain features. In the southern portion of the region the new snow sits on a crust/facet combination along with old wind slabs on lee slopes. In the northern part of the region one can add surface hoar to the crust/facet/slab combination. Recent snowpack tests generally give moderate sudden "pops or drops" shears on this weakness and show potential for wide propagation. The mid and lower snowpack are generally strong and well-settled. Although basal facets and depth hoar are likely to exist in the north of the region, giving us a low probability, but high consequence of a large destructive avalanche.

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.