Avalanche Forecast

Issued: Dec 12th, 2012 9:25AM

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

slemieux, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

A weak system will cross the region during Thursday and bring light precipitations and moderate to strong winds from the South West. Temperatures will stay cool for the entire period. Friday should see some sunny periods with lighter winds from the North West. Later Saturday, another upper trough is expected to spread moderate snow accumulations over the region with moderate winds from the South.

Avalanche Summary

Several natural slab avalanches up to size 2 have been reported on various aspects in the storm snow. A few skier triggered loose dry avalanches have also been reported on steep terrain.

Snowpack Summary

30 cm of fresh snow has been transported by West and South West winds in the alpine and treeline creating the windslab problem on lee slopes. It has been reported that these windslabs are reactive under the weight of a skier. In sheltered areas, this new snow could also be burrying older and deeper windslabs in the alpine. Sluffing is still an issue on steep features protected from the wind below treeline. Below treeline, also watch for early season obstacle, such as stumps and creeks. The deep persistent instabilities (surface hoar and early November crust) located in the middle and near the bottom of the snowpack are still a concern in this region, however, we haven't had report of their sensitivity or reactiveness. Digging down and making your own observations will be critical to safe slope selection. Any observations from the field are welcome at forecaster@avalanche.ca.

Problems

Wind Slabs

Expect buried windslabs in sheltered area and newly formed windslabs in exposed lee slopes and cross-loaded gullies below ridge crests.

Use ridges or ribs to avoid pockets of wind loaded snow.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Deep Persistent Slabs

Be extra careful in areas where ground roughness is not present to act as anchorage. Smooth ground cover areas include firn on glaciers, grassy slopes and rock slabs.

Common trigger points for this type of layer is shallow-rocky snowpack areas and areas with smooth ground cover.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Dec 13th, 2012 2:00PM