Avalanche Forecast

Issued: Jan 16th, 2013 9:26AM

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

pgoddard, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Thursday: Moderate to strong W winds. Alpine temperature near -2. Trace of snow.Friday: Light to moderate NW winds. Alpine temperature near -11. No snow.Saturday: Light SW winds. Alpine temperature near -3. No snow.

Avalanche Summary

Several naturally-triggered size 1 wind slabs were observed on Tuesday. A skier also triggered a size 1.5 slab on a north aspect at 1300 m, which failed on buried surface hoar.

Snowpack Summary

Strong north to north-westerly winds have left wind slabs in many areas, even at treeline. Settled storm snow sits above surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of these weaknesses is patchy, but where they exist, it may still be possible to trigger a large avalanche with the weight of a person or snowmobile. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

Wind Slabs

Wind slabs may be found behind terrain breaks such as ridges and ribs. It may be possible for a wind slab to step down to deeper instabilities.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>Use ridges or ribs to avoid pockets of wind loaded snow.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Persistent weaknesses are buried at a prime depth for human triggering. Triggering persistent slabs is most likely on south-facing slopes and in sheltered terrain below treeline.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Jan 17th, 2013 2:00PM