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Avalanche Forecast

Archived

Nov 30th, 2012–Dec 1st, 2012

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

Regions

Little Yoho.

Decent ski quality reported in sheltered locations at treeline.  SH

Weather Forecast

5-10cm at TL by Sat. night and light amounts through to Monday.  We may see increased alpine SW flow Sat. with freezing levels up to 1600-1700 during the day.  Possibly rain in lower elevation areas W of divide such as Field.

Snowpack Summary

Sunshine study plot CTH24RP on Nov. 6 CR approx. 20 cm above ground.  Crust is breaking down.  Small SH noted (3mm) 10cm below surface.  90-100cm at TL in most areas, and average 5cm HN24 with little wind effect

Avalanche Summary

Lake Louise ski hill had no results from explosives control in alpine terrain.  No other avalanches observed.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

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.