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Avalanche Forecast

Archived

Mar 5th, 2014–Mar 6th, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Banff Yoho Kootenay.

With the recent new snow and high uncertainty with the deeper layers now is the time for conservative decision making.

Weather Forecast

The storm will continue through to Thursday evening with another 15 cm forecasted. High temperatures in the alpine around -3 with light winds. Mixed sun and cloud with some flurries on Friday.

Snowpack Summary

Sunshine, Kootenay and Yoho areas have received thirty to 40 cm of storm snow since March 2.  Lesser amounts around Lake Louise and Bow Summit. Forty to 80 cm of settled snow on the Feb 10 interface is producing moderate sudden planar results. Fresh windslabs up to 40 cm deep in alpine are reactive to skier control.

Avalanche Summary

Numerous skier controlled winds-slabs 40-60 cm deep up to size 2 reported from Sunshine. Two significant skier triggered avalanches (Class 2 and 2.5) reported at 1700 m (east aspect) in Kootenay. These initiated 50-100 cm down on the Feb 10 interface and propagated up to 100 m. This suggests that the Feb 10 layer may be getting overloaded.

Confidence

Forecast snowfall amounts are uncertain on Thursday

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.