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Avalanche Forecast

Archived

Dec 1st, 2012–Dec 2nd, 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, 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.

Regions

Banff Yoho Kootenay.

Good skiing can be found at sheltered treeline elevations.  Watch for sloughing in very steep gullies if winds pick up. SH

Weather Forecast

2-5cm Sunday with mainly light-mod. S-SW winds forecast. and freezing levels up to 1500-1600m .  Alpine winds may spike Sunday evening in to Monday.

Snowpack Summary

Bow Peak Hwy93 N @2400m HS 95. CTHRP results on Nov6 CR prominent 20cm off of ground.  5cm HN24 in most locations being redistributed mainly from SW winds forming thin wind slabs on lee aspects at ridgetop. Facetting of snowpack winning in many areas

Avalanche Summary

When winds picked up there was a sz 1.5 sluff out of steep ski terrain in the Granddaddy couloir on Bow Peak.  Not much mass but would have flushed a skier or climber.  Lake Louise ski hill had no results bombing in previously uncontrolled terrain.

Confidence

Wind effect is extremely variable

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.