Avalanche Forecast

Issued: Jan 20th, 2015 4:03PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

We cautiously drop the treeline danger rating to Moderate, but expect that human triggered avalanches remain likely in many areas at treeline and above. Don't let the lack of natural avalanche activity fool you. Travel carefully.

Summary

Weather Forecast

The westerly flow continues with no snow in the forecast until early Thursday morning. Treeline temperatures on Wednesday will range from -4 to -8 with alpine winds increasing to 50-70 km/hr by the afternoon. A total of 5 cm of snow is expected by Friday.

Snowpack Summary

The snowpack remains fundamentally weak, with a combination of windslab, surface hoar and basal facets all causing concern in different types of terrain. Snowpack tests continue to produce moderate, sudden results on the Dec 18 layer down 40 cm from the surface.Â Human triggering is likely.

Avalanche Summary

No natural avalanches observed, but human and explosive triggered avalanches persist.Â Yesterday someone in the Sunshine Village backcountry triggered a windslab that took them for a 50m ride. Avalanche control on Mt Dennis in Field today produced no slabs, but loose snow avalanches ran 1000m over Pilsner Pillar.

Confidence

Problems

Wind Slabs

Surface windslabs formed on Jan 18/19 can be triggered by skiers and climbers. Feel for tension in the surface snow and avoid freshly windloaded terrain.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

The distribution of this layer is difficult to follow, but assume it exists in the snowpack and look for it in the upper 40 cm.

Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

In shallower snowpack areas (most of the region) the weak base of the snowpack persists and could be triggered in steep, rocky terrain features. This problem will persist for some time, give it careful consideration before entering serious terrain.

Avoid thin, rocky or sparsely-treed slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Jan 21st, 2015 4:00PM