Avalanche Forecast

Issued: Jan 30th, 2012 9:41AM

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

ccampbell, Avalanche Canada

Cariboos.

Summary

Confidence

Good - -1

Weather Forecast

Tuesday: Light snowfall with moderate southwesterly winds and freezing levels near valley bottoms. Wednesday: A clearing trend with freezing levels as high as 1000m. Thursday: A temperature inversion with associated valley cloud is possible.

Avalanche Summary

Reports are coming in about a widespread natural avalanche cycle that occurred Saturday night and Sunday morning with very large avalanches running full-path on all aspects and elevations. Storm slabs continued to be highly sensitive to human triggers on Sunday with slope-cut avalanches up to Size 2 on steep unsupported features and gullies at treeline and below.

Snowpack Summary

Recent warm temperatures and upside-down storms created a touchy surface slab. Other weaknesses exist within and under the 150+cm of recent storm snow, but things seem so be settling rapidly. Moderate southerly or southwesterly winds have created wind slabs and large fragile cornices in exposed lee and cross-loaded terrain. All this new snow increases the load (stress) on deeper layers created during the mid-January cold snap; namely facets (sugar) and a crust at lower elevations (say 1500m and lower). This layer is now deeply buried (around 200 cm or more in many places) but snowpack test results on this layer range from no result to easy (variable strength) but the shear pops (if triggered it wants to propagate).

Problems

Wind Slabs

Wind slabs are generally lurking below ridgecrests, behind terrain features and in cross-loaded gullies. They can fail as very large, destructive avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 6

Storm Slabs

Large storm slab avalanches have been occurring for the past week and are expected to remain sensitive to triggers for the forecast period.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Cornices

Large cornices are looming over many slopes. A falling chunk could trigger an avalanche on the slope below.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

The Jan 20 and Jan 13 layers are starting to blend. Doesnèt matter - theyère pretty similar it seems. Large planar slopes at 1500m and below.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

4 - 7

Valid until: Feb 1st, 2012 3:00AM