Avalanche Forecast

Issued: Feb 24th, 2013 8:46AM

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.

Peter, Avalanche Canada

Cariboos.

Summary

Confidence

Fair

Weather Forecast

Synopsis: A weather system affecting the region on Sunday will move out and leave behind unsettled conditions for Monday. A ridge of high pressure is expected to form and give drier conditions with sunny breaks for late Monday and Tuesday. Overnight and Monday: Continued moderate to locally heavy snowfall – 10-20 cm through Monday. The freezing level is around 900 m during the day and winds are moderate from the southwest, easing to light from the west.Tuesday: A mix of sun and cloud. The freezing level is around 800 m and winds are light from the southwest.Wednesday: Light to moderate snow. The freezing level should remain near 800 m.

Avalanche Summary

Surprisingly there were few reports of slab avalanches from the region over the past couple days. Just to the southeast in the northern Monashees and Selkirks there was a fairly widespread natural avalanche cycle in response to heavy snow and strong wind on Friday.

Snowpack Summary

40-70 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 60-80 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. 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 may exist within the recent storm snow and may be triggered by additional loading. Expect deep and dense wind slabs in exposed north through southeast facing terrain at and above treeline.

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

Likely - Very Likely

Expected Size

1 - 4

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.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 6

Valid until: Feb 25th, 2013 2:00PM