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Avalanche Forecast

Archived

Nov 16th, 2012–Nov 17th, 2012

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

Regions

Little Yoho.

High winds, mild temp's, and anywhere from 5-20cm will increase the avalanche danger by Sunday. Pay particular attention to areas of heavier snowfall.

Weather Forecast

On Saturday, winds and temp's are expected to rise, with strong/extreme SW winds and freezing levels up to 1900m midday. 15cm possible by Saturday night in northern areas of region (Bow Summit). Sunday, cooling with continued strong winds and 5-10cm.

Snowpack Summary

Continued settling of the surface snow over the Nov crusts, which are buried 20-50cm below the surface.  The surface snow varies from soft to hard slab in lee features, while some unconsolidated snow still exists in sheltered locations.  Below the crusts, a settled base exists.

Avalanche Summary

No new observations in Yoho today. Ski hill avalanche control on Sunshine and Lake Louise produced no notable results.

Confidence

Forecast snowfall amounts are uncertain

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.