Avalanche Forecast

Issued: Dec 24th, 2011 9:01AM

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

Avalanche Canada pgoddard, Avalanche Canada

Click on the 'Forecaster's Blog' link below for more discussion on how to safely approach backcountry travel under the current conditions.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Sunday: Light to moderate snowfall through the day, with the freezing level near 1000m. Strong south-westerly winds at ridgetop. Storm snow totals should reach around 15cm on average by Sunday, with local variations. Expect enhanced amounts on the western side of the range.Monday: Moderate precipitation at times, with the freezing level slowly rising to 1200m. Moderate-strong south-westerly winds.Tuesday: Confidence for Tuesday's weather is limited, but we're currently expecting moderate snowfall at times, with a rising freezing level.

Avalanche Summary

No new avalanches have been reported since Wednesday. It's a big area, however, and we receive limited reports. Earlier in the week, a natural avalanche cycle was observed in the South Cariboos, mostly on north aspects in the alpine. Several rider-triggered avalanches occurred, with the mid-December hoar/facet/crust interface causing most concern. With new storm slabs and wind-slabs building over these known weaknesses, further avalanche activity remains a distinct possibility.

Snowpack Summary

Recent storm snow continues to be redistributed by southwest winds. Wind slabs with the potential to propagate widely exist in the alpine, particularly on north through east aspects. At treeline and below, pockets of wind slab also exist in open areas. A surface hoar/facet/crust interface is buried anywhere from 30- 80cm deep and has recently proven itself to be variable in its distribution, with concerning (sudden planar) results in snowpack tests and rider-triggered avalanches in some places and little results in other places. This means the problem is somewhat spotty, but could be lurking round the corner - and have huge consequences if triggered.A resistant-type shear about 30cm down within the recent storm snow also exists. A sun crust also exists in the alpine on steep south and west aspects. The mid-pack is generally strong and well settled.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs exist on lee and cross-loaded features and are expected to build further over the next few days.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

An icon showing Persistent Slabs
A cohesive slab exists above the early December buried surface hoar/facet interface. This weakness may produce wide propagations. Deeper persistent weak layers also exist.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Dec 25th, 2011 8:00AM