Avalanche Forecast

Issued: Dec 8th, 2013 8:10AM

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

swerner, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

The strong arctic high will gradually start to break down. Weak frontal waves will cross the interior regions, bringing some cloud cover and light snowfall amounts.Monday: Mix of sun and cloud. Alpine temperatures show a high of -14. Ridgetop winds will blow moderate from the West. Tuesday: Cloudy with some sunny periods. Alpine temperatures show a high of -13. Ridgetop winds will blow light from the West. Snow amounts near 5 cm.Wednesday: Cloudy with sunny periods. Alpine temperatures show a high of -11. Ridgetop winds will blow light from the West. Snow amounts 3-5 cm.

Avalanche Summary

In the Northern part of the region a natural wind slab, size 1 was reported on a NW aspect. Additionally numerous size 1 loose dry avalanches from NW aspects were easily rider triggered. Loose dry avalanches are small, but they may be consequential if you're caught or pushed into depressions or off cliffs. Watch your sluff, and deek out to the side to escape.

Snowpack Summary

Strong NE winds after the storm have caused reverse loading and wind slab formation on SE through W aspects on open slopes and behind terrain features.Widespread surface hoar development and surface facetting exists. Snowpack depths at treeline vary across the region, averaging 70-110 cm. In the Southern part of the region there is 40-70cm of new snow over the late-November surface hoar/ crust/ facet interface that may be reactive, especially in sheltered northerly aspects where the surface hoar was better preserved.In the Northern part of the region the lower/mid snowpack is fundamentally weak, composed of an early season crust (more prevalent on north aspects) and weak faceted crystals above and below the crust. This persistent slab may be stubborn to trigger, but if triggered have high consequences.

Problems

Wind Slabs

Strong winds from the North have redistributed snow forming hard and soft wind slabs in exposed lee terrain. Wind slabs found on these aspects are not typical, and they may surprise you.

Avoid freshly wind loaded features.>Avoid traveling in areas that have been reverse or cross-loaded by winds.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

In deeper snow areas, it may be possible to trigger an avalanche on a layer of buried surface hoar. In shallower ones, watch for a weak sugary facet layer near the base of the snowpack.

Conditions have slightly improved, but be mindful that deep instabilities still exist.>Dig down to find and test weak layers before committing to a line.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 9th, 2013 2:00PM