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Avalanche Forecast

Archived

Dec 30th, 2014–Dec 31st, 2014

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

Regions

Little Yoho.

The cold snap is over with warming occurring today. Of note is the temperature inversion, and tomorrow's high of -5 at higher elevations should cause ice climbers to carefully consider their overhead hazard - it will be a hot afternoon in the sun.

Weather Forecast

The ridge of high pressure has one more day left in it, and Wednesday will be sunny with alpine temperatures reaching -5. Starting Thursday a system embedded in a NW flow will cross the area, but only light amounts of snow are expected. Trace for Thursday, then 4cm each day for Fri and Sat. Temps will be in the -5 to -10 range with light west wind.

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 located 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.

Confidence

Due to the number and quality of field observations

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.