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Avalanche Forecast

Archived

Nov 11th, 2012–Nov 12th, 2012

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

Regions

Little Yoho.

Early season conditions exist. Go easy. The larger avalanches observed on steep northerly slopes indicate things may be more touchy in the high alpine.. JBW

Weather Forecast

Westerly flow will develop with warming temperatures and light snowfall. Wind transport in open areas likely. Temps -4 to -10 Winds SW 20-40km/hr

Snowpack Summary

Lots of wind effect and wind slabs n open areas. Some slabs pulling out on Nov 6th Crust which is down approx 30cm. Crust is absent above 2700m. Snowpack is 1F and supports skiers at and above treeline. (Depth 60-120cm)

Avalanche Summary

Some controlled (Sc/Xe) slabs in uncontrolled areas at ski hills up to size 2: 30-60cm thick failing on Nov 6 crust. Several larger size 2-3 slabs observed today failing on firn snow about 1meter down in alpine locations along Wapta traverse

Confidence

Intensity of incoming weather systems is uncertain on Tuesday

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.