Avalanche Forecast

Issued: Feb 20th, 2013 8:38AM

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 pmarshall, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

Synopsis: A series of frontal systems is expected to affect the region over the next few days bringing steady moderate precipitation and seasonal temperatures.  Thursday: Light to moderate snowfall – 5-10 cm. Winds are moderate and gusty from the west-southwest. The freezing level is around 900 m. Friday: Moderate to locally heavy snowfall – 20-30 cm. Winds are strong from the southwest and the freezing level is around 700 m. Saturday: Cloudy with flurries or light snow. The freezing level is steady at 700 m and winds ease to light from the northwest.

Avalanche Summary

A new size 2.5 natural avalanche was reported on the east side of the region. This event occurred on a south aspect in the alpine and likely failed on a sun crust, down approximately 40 cm.

Snowpack Summary

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. New wind slabs developed at treeline and above due to the new snow and wind during the storm. These soft new wind slabs (hard slabs in some areas) are reported to be reactive and may be hiding stiffer wind slabs that are a couple of days older. 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, or a cornice fall.

Problems

Wind Slabs

An icon showing Wind Slabs
Fresh wind slabs may form on exposed north through east aspects near ridge tops and behind terrain features. These could be triggered by the weight of a rider.
Be cautious as you transition into wind affected terrain.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
Up to 40 cm of settled storm snow sits on the Feb. 12 surface hoar or sun crust. Additional loading from snow and wind or the weight of a person could be enough to trigger this weak layer.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 21st, 2013 2:00PM

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