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Avalanche Forecast

Archived

Jan 30th, 2013–Jan 31st, 2013

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

Regions

Little Yoho.

The major concern today is the potential to trigger windslabs in steep unsupported trerrain. In Kootenay another concern is a buried surface hoar layer down 55.

Weather Forecast

Cool NW flow will give way to a warm westerly flow with the chance of some light snow showrers and mod to strong winds.

Snowpack Summary

In alpine there is 20-25 cm of recent storm snow sitting on previous hard wind slabs and wind pressed snow. Some soft slab development in lee terrain near ridge tops. In shallow snow pack areas the mid-pack is facetting and losing strength. In the south west (Kootenay) there is a buried surface hoar layer down 55 cm that is a concern.

Avalanche Summary

Forecasters observed a size 2 naturally triggered avalanche on a N aspect around 2300m on the Sunshine road in the last 48 hrs. A natural Icefall avalanche ran off the north face of Mt. Stephen today and just covered the train snow shed. A natural 1.5 was observed on the NE slope of Dolomite peak.

Confidence

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.