Avalanche Forecast

Issued: Jan 4th, 2012 9:31AM

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

ccampbell, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Good - -1

Weather Forecast

5-10cm possible overnight Wednesday, with another 5-10cm expected on Thursday. Freezing levels could reach as high as 2000m Wednesday evening before dropping to 1200m on Thursday with continued strong southwesterly winds. Friday and Saturday should be mostly dry with freezing levels back to valley bottoms and light westerly winds.

Avalanche Summary

There are two recent reports of skiers remotely triggering avalanches running on the mid-December surface hoar. One was relatively small on a steep lee slope triggered from a ridge 10m away. The other was a 30-80cm thick Size 2 that was triggered by a cornice fall, which was remotely triggered from a skier 3m away on the ridge crest.

Snowpack Summary

New snow and gusty winds are keeping wind slabs and cornices fresh and weak, and in some places buried old wind slabs are a concern. A lightly buried thin crust extends into treeline elevations. Compression tests have been producing easy to moderate sudden results on the mid-December surface hoar, down 30-80cm, and propagation tests and whumpfing have shown that avalanches associated with this persistent slab have a high propensity to propagate over large areas. Other weaknesses within the slab create the potential for step-down avalanches. Basal facets and depth hoar remain a concern in shallow rocky areas.

Problems

Persistent Slabs

Persistent weaknesses remain susceptible to human-triggers, including remote triggering. Although cooling temperatures throughout the forecast are period

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Wind Slabs

Fresh wind slabs are lurking below ridge crests, behind terrain features, and in cross-loaded gullies. New cornices are also weak.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Jan 5th, 2012 8:00AM