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Avalanche Forecast

Archived

Nov 25th, 2012–Nov 26th, 2012

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

Regions

Little Yoho.

There is still a chance of triggering a large slide in the right terrain feature as wind loading and settling stiffen up the slab. Stick to moderate terrain and travel is good. JBW

Weather Forecast

Little in the way of precipitation for Monday. Skies become cloudy and then a chance of flurries and some moderate accumulations through midweek with a westerly flow. Artic front and some upslope by Thursday.

Snowpack Summary

Still very little wind effect in last weeks storm. Storm snow is approx. 40 cm. Stellar layer under Hst down approx 30-50 and Noc Cr down 60-80 are major layers. Relatively well settled snowpack for end of November.

Avalanche Summary

Avalanche control in Yoho on Bosworth and Stephen produced thin storm snow slabs up to size 2 none stepping down. Wind loading on NE face of Rundle produced a size three natural likely on Nov crust.

Confidence

Intensity of incoming weather systems is 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.