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Avalanche Forecast

Archived

Dec 31st, 2014–Jan 1st, 2015

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

Regions

Little Yoho.

HAPPY NEW YEAR!  The incoming weather system Friday-Sunday may bring enough snow and wind to bump up the hazard on the touchy surface hoar layer.  Watch for slab development on this layer.

Weather Forecast

Cloudy with light flurries for Thursday, highs of -6C.  A low moving down from the NW will bring flurries starting Thursday night through to Sunday. A total of 22 cm may fall.  The change may be gradual, but the combination of snow & wind will make the surface hoar layer more susceptible to triggering & we may start to see some natural activity.

Snowpack Summary

With a total snowpack depth of just over one meter, two weaknesses exist within this snowpack. The Dec 18 surface hoar layer is alarmingly reactive down approximately 30 cm, and while there is no slab overlying it now we expect problems with subsequent snowfalls (or winds). Additionally the base of the snowpack is weak with facets and depth hoar.

Avalanche Summary

No new avalanches have been observed or reported. A large settlement was observed on the Dec 18 surface hoar down 30 cm by a group en route to Isolated Col.

Confidence

Intensity of incoming weather systems is uncertain

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.