Avalanche Forecast

Issued: Jan 7th, 2013 9:49AM

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

mpeter, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Tuesday: Cloudy, with precipitation building late in the day as a surface low approaches. Winds should be westerly 50-70km/h and freezing levels may climb to 1000m.Wednesday: The surface low should bring moderate to locally heavy snowfalls. Freezing levels may reach 1500m as the low advances with southwest winds reaching 60km/h.Thursday: The low should pass leaving occasional flurries and eventually sunny breaks. Winds turn northeasterly and diminish to 20km/h.

Avalanche Summary

Isolated windslabs in lee terrain to size 1.0 and continued sluffing in steep terrain to size 1.0.

Snowpack Summary

Up to 15cm of low density new snow has fallen recently. Moderate south/southwest winds have redistributed this new snow into small windslabs in immediate lee features in the alpine and exposed treeline.The January 4th interface consists predominantly of loose facets up to 30cm deep. In isolated locations (sheltered treeline and below treeline) surface hoar up to 12mm is present. There is a 1-3cm sun crust on steep south and west facing terrain. Above this interface is another surface hoar layer, creating a reactive sandwich of weak crystals. The storm snow is bonding poorly to this interface.The midpack is well bonded and strong. The November 28 surface hoar is still being found in isolated, sheltered below treeline locations buried 95-120cm. The deep crust/facet combo from early November still exists and concern remains (although unlikely) for triggering from a shallow spot.

Problems

Wind Slabs

New windslabs have formed in immediate lee and cross loaded locations. The forecasted winds are quite strong, meaning more intense slab development.

Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Storm Slabs

I consider sluffing to be part of this problem. Where the storm snow is still shallow (less than 20cm) expect continued sluffing, but warming temperatures will promote settlement of deeper storm deposits into cohesive storm slabs.

Be cautious of sluffing in steep terrain.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Jan 8th, 2013 2:00PM