Avalanche Forecast

Issued: Feb 7th, 2012 9:20AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada ccampbell, Avalanche Canada

Summary

Confidence

Good - -1

Weather Forecast

Wednesday: A weak weather system is expected to pass through the region in the morning bringing a few flurries and moderate westerly winds mainly over the West Kootenays. Freezing levels are expected to rise to 1000 m in the afternoon. Thursday and Friday: A series of weak frontal systems are expected to bring 3-10cm to the region each day starting Thursday afternoon, but the timing is uncertain. Freezing levels could reach as high as 1500m.

Avalanche Summary

One notable Size 2 skier triggered avalanche occurred outside the ski area boundary near Whitewater. This was on a North aspect @1985m. It was a variable 40-60cm thick slab in cross-loaded terrain and 2 skiers were involved, but sustained no injuries. Check out the incident database (under the Bulletins tab) for other reports of recent avalanche involvements in the region, and search vimeo.com for helmet-cam footage of the Feb. 3rd incident near Nelson.

Snowpack Summary

The current snow surface is well on its way in becoming a dangerous weak layer once a sufficiently cohesive slab develops. Surface hoar is continuing to develop on sheltered slopes at all elevations combined with near-surface facets at lower elevations and surface crusts on sun-exposed slopes. There is still dry snow on northerly aspects at higher elevations, but it is likely wind-affected and variable in exposed areas. Mid-day pin-wheeling and other signs of moist snow have been observed on solar aspects at and above treeline. A couple of thin crusts down 30-50cm have been producing moderate to hard shears in tests. Some areas are still getting sudden planar shears on the mid-December surface hoar layer. Basal facets were responsible for a large whumpf on a shallow south facing treeline slope in the Rossland Range and gave very easy and sudden compression tests results where they were found down 60cm.

Problems

Wind Slabs

An icon showing Wind Slabs
Weak wind slabs could be lurking below ridge crests and behind terrain breaks. Watch for reverse-loading from easterly winds, and highly variable cross-loaded slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Very large avalanches remain a concern in shallow rocky areas with heavy triggers, such as cornice falls and step-down avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Feb 8th, 2012 8:00AM