Avalanche Forecast

Issued: Feb 25th, 2013 9:12AM

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

Peter, Avalanche Canada

Cariboos.

Summary

Confidence

Good

Weather Forecast

Synopsis: A brief ridge of high pressure is expected to form and give drier conditions with sunny breaks for Tuesday. The next system reaches the coast on Tuesday and spreads more cloud and light precipitation to the Interior by Tuesday night. Tuesday: A mix of sun and cloud. The freezing level is around 1000 m and winds are light to moderate from the southwest.Wednesday: Increasing cloud and light snow. The freezing level should remain near 1000 m. Thursday: Mainly cloudy with light snow. The freezing level is around 1000 m and winds are generally light from the southwest.

Avalanche Summary

There are several reports of natural slab and loose snow avalanches up to size 2. There are also a few reports of avalanches being triggered from a distance and failing on the February 12 surface hoar layer. Most of these events occurred below treeline in north facing terrain.

Snowpack Summary

50-90 cm of new snow has fallen in the past few days. Strong west-southwest winds have redistributed the new snow into deep wind slabs on exposed lee slopes and cross-loaded gully features. The February 12 persistent weak layer (crust, and/or surface hoar) is now down 60-90 cm and is primed for triggering. Recent snowpack tests have shown easy to moderate "pops" results on this interface and has been particularly touchy on south aspects where a sun crust exists. Widespread whumpfing has also been reported. 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

Persistent Slabs

Additional loading from snow and wind, or the weight of a rider could be enough to trigger the February 12 persistent weak layer. This layer seems most reactive at and below treeline.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Wind Slabs

Expect deep and dense wind slabs in exposed lee and cross-loaded terrain. Also, cornices have grown large and weak and may fail with additional growth or during periods of sunny weather.

Be cautious as you transition into wind affected terrain.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 26th, 2013 2:00PM