Avalanche Forecast

Issued: Feb 21st, 2013 8:20AM

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

pmarshall, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Timing of incoming weather is uncertain

Weather Forecast

Synopsis: A series of frontal systems is expected to affect the region over the next few days. The strongest system is on track for Friday. Friday: Moderate to locally heavy snowfall – 20-30 cm. Winds are strong from the southwest and the freezing level is around 1000 m. Saturday: Cloudy with flurries or light snow. The freezing level is near valley bottom and winds ease to moderate from the northwest. Sunday: Moderate snow. The freezing level is around 700 m.

Avalanche Summary

There are no new reports of natural avalanches from the region. Rider triggered avalanches are limited to a couple size 1 slab avalanches in steep north facing terrain. This will likely change over the next few days with forecast snowfall and strong winds. Expect both the size and likelihood of avalanches to increase.

Snowpack Summary

New wind slabs are likely in exposed north through east facing terrain at and above treeline. Variable amounts of new snow continue to add to the recent storm slab which sits above the February 12th weak surface hoar layer and a sun crust on solar aspects. This layer is now buried down about 30-60 cm deep depending on where you are in the region. Recent snowpack tests have shown easy to moderate "pops" results in this interface. Deeper persistent weak layers from early February and late January continue to show planar failures when moderate to hard forces are applied in snow pack tests. These deeper layers have not been reactive to the weight of a rider, but they may be triggered by large loads like an avalanche in motion (step-down avalanche), or a cornice fall.

Problems

Storm Slabs

Weaknesses could exist within or under the new storm snow. In addition, expect new wind slabs to form on north through east facing slopes near ridge tops.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Stick to non-avalanche terrain or small features with limited consequence.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

Persistent Slabs

Additional loading from snow and wind, or the weight of a person could be enough to trigger the February 12 persistent weak layer.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Valid until: Feb 22nd, 2013 2:00PM