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

Regions

Kootenay Boundary.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

Thursday: Moderate NW winds. Alpine temperature near -4. Light snow.Friday: Light W winds. Alpine temperature near -2. No snow.Saturday: Light W winds. Alpine temperature near 0. Sunny skies, with valley cloud.

Avalanche Summary

Size 1 to 2 loose dry avalanches have been failing with natural and human triggers in steep terrain. A few slabs to size 2 have also been observed, in some cases failing on a crust/facet interface below recent storm snow.

Snowpack Summary

NW winds have redistributed 15-40 cm of recent snow into soft or hard slabs on lee slopes in the alpine and at treeline. In areas not affected by the wind, loose snow is sluffing easily in steep terrain. The new snow sits on a variety of old surfaces including surface hoar, facets, hard slabs and crusts. Deeper, about 50-60cm down, a weak interface buried in early January exhibits moderate to hard, sudden results in snowpack tests. The snowpack below this is generally well bonded.

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.