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Avalanche Forecast

Archived

Jan 12th, 2014–Jan 13th, 2014

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

Regions

South Rockies.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Tonight and Monday: Light to moderate precipitation amounts are expected tonight with extreme W winds. Freezing levels are expected to rise to 1200 m on Monday. Tuesday: An upper ridge is building over the region which will give the storm pattern a break. Trace accumulations, a mix of sun and cloud, strong W winds and freezing levels rising to 2000 m. Wednesday: The ridge brings dry, clear and warm temperatures over the Southern part of the province with strong winds from the NW.

Avalanche Summary

Multiple avalanches were reported yesterday up to size 3 on slopes lee of wind, some of which are suspected to have stepped down to deeper instabilities.

Snowpack Summary

Accumulations forecasted tonight and strong W winds is keeping avalanche conditions dangerous for tomorrow. The new windslabs lee of W winds below ridgetop will most likely be very touchy and could possibly slide naturally. Watch for loose snow avalanches in steeper terrain as well. Cornices will continue building and could fall possibly triggering big avalanches that could step down to deeper layers. The late November facet/crust and surface hoar layer down between 70-100 cm and the depth hoar and basal facets situated at the bottom of the snowpack are suspected to have reacted to the recent storm load and avalanches may have stepped down to these layers. These persistent weak layers are showing a high spatial variability and also some variable snowpack and sledding test results. In other words, they are spotty and hard to predict. The facet/crust layer at treeline has been mostly reactive on E aspects and the depth hoar layer in the alpine is still concern especially where the snowpack is thinner.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.