Avalanche Forecast

Issued: Feb 22nd, 2013 8:27AM

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

Good

Weather Forecast

Synopsis: There is a brief break between weather systems on Saturday before the next frontal system arrives late Sunday and into Monday. Saturday: Cloudy with light snow in the morning and gradual clearing through the day. The freezing level is near valley bottom and winds ease to moderate from the west-northwest. Sunday: Moderate snow – around 10 cm. The freezing level is near valley bottom and winds are moderate from the west. Monday: Snow easing in the morning with gradual clearing throughout the day. The freezing level remains near valley bottom.

Avalanche Summary

Avalanche activity on Thursday was primarily limited to loose dry avalanches in steep terrain, indicating that a slab had not yet formed. This has almost certainly changed today. Heavy snow and strong winds on Friday will likely result in a natural avalanche cycle which should continue into the weekend.

Snowpack Summary

By late Friday morning there was already up to 30 cm of new snow on the ground. This new snow was accompanied by strong west-southwest winds forming weak wind slabs in exposed lee terrain. The February 12 persistent weak layer (crust, and/or surface hoar) is now down 60-80 cm and is primed for triggering. Recent snowpack tests have shown easy to moderate "pops" results on 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

The new snow may not bond well to the previous surface and may overload buried weaknesses in the top 100 cm. In addition, expect new wind slabs to form in exposed north through east facing terrain and cross-loaded gullies.

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.>

Aspects: All aspects.

Elevations: All elevations.

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.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Valid until: Feb 23rd, 2013 2:00PM