Avalanche Forecast

Issued: Jan 20th, 2014 8:45AM

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

bcorrigan, Avalanche Canada

South Rockies.

Summary

Confidence

Good - Due to the number and quality of field observations

Weather Forecast

No precipitation in sight for the next few days. The ridge of high pressure continues to dominate the weather pattern blocking Pacific moisture from the Pacific Northwest.Tuesday: Nil precipitation wind SW at ridge tops, freezing level at 1500m.Wednesday: Chance of light precipitation or flurries, winds from the N-NW, freezing level to 1600m.Thursday: NIl precipitation, winds light at ridge tops, freezing level to 1500m.

Avalanche Summary

Report of a size 2.5 snowmobile triggered avalanche in steep shallow snowpack, failing to ground level. We suspect this to have failed on the Nov 30th surface hoar, then stepping down to the basal facets ( surface hoar). Areas of shallow snowpack are of special concern, as well as areas where there is a hazard from above such as cornices or steep south facing cliffs. High temperatures at upper elevations may increase the chance of triggering from surface sluffing or cornice failure.

Snowpack Summary

Extensive wind transport and wind slab development has occurred in all areas of the region. Recent storm snow varies from 40-70 cm across the region and in some alpine areas storm slabs are more than a metre thick. Persistent weak layers of buried crusts/facets/surface hoar continue to be a concern, and may have been the failure plane for recent large natural avalanches. Surface facetting and surface hoar growth throught the forecast region on northerly and protected aspects. Strong solar radiation and above-freezing temperatures producing sun crust on solar aspects.

Problems

Wind Slabs

Wind continues to build hard slabs in the alpine and at tree line, very warm temperatures and strong solar radiation may increase the likelihood of triggering. A cornice failure or radiation sloughing in cliffs could trigger lower slopes.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>Watch for areas of hard wind slab in steep alpine features.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

Storm snow and hard wind slabs have been added to the load above buried weak layers. Deeply buried weak layers may become harder to trigger, but the consequences could be very large destructive avalanches.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Make observations and assess conditions continually as you travel.>Be aware of the potential for large, deep avalanches due to the presence of buried facet/crust layer and depth hoar layer.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Cornices

Cornices may become weak and fail naturally with the strong solar radiation and warm alpine temperatures. Cornice falls are a large load that may trigger buried persistent weak layers on slopes below, resulting in very large avalanches.

Avoid steep slopes below cornices.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Jan 21st, 2014 2:00PM