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Avalanche Forecast

Archived

Dec 20th, 2013–Dec 21st, 2013

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

Regions

Jasper.

Hazards lurk just below the surface as early season conditions persist. Snowpack depth remains variable across the landscape. 

Weather Forecast

Flurries will occur through weekend with seasonal temperatures ranging from -12 to -20. Temperatures may warm up to -5 on Monday bringing with it 10-15cm and moderate-strong SW winds.

Snowpack Summary

Turbulent winds continue to add to the variable snow distribution at treeline and above. Wind slabs are developing in lee terrain features. These windslabs sit above the sporadically distributed October 27 raincrust with weak facets at the bottom of the snowpack. Colder temperatures are tightening the snowpack but at same time promoting faceting.

Avalanche Summary

Thursday, a size 1.5 slab occurred at 1800m on an Easterly slope. This was a thin windslab over basal facets and ran to ground. Visibility was reduced to valley bottom on Friday.

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.