Avalanche Forecast

Issued: Dec 9th, 2013 8:02AM

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 - Intensity of incoming weather systems is uncertain

Weather Forecast

The arctic ridge will continue to persist today. By mid- week, a significant change will take place in the current weather pattern as a pacific frontal system brings precipitation, warmer temperatures and strong winds from the West.Tuesday: Mainly cloudy with some sunny periods. Alpine temperatures show a high of -13. Ridgetop winds light from the NW.Wednesday: Mainly cloudy with snow amounts up to 5 cm. Alpine temperatures show a high of -10. Ridgetop winds moderate from the West.Thursday: Cloudy with snow amounts 3-5 cm. Alpine temperatures show a high of -9. Ridgetop winds light from the SW.Higher snowfall amounts may occur in the central part of the region.

Avalanche Summary

No recent avalanche observations have been reported.

Snowpack Summary

Strong NE winds have reverse loaded and formed isolated wind slabs on SE through West aspects behind terrain features and on open slopes.Widespread surface hoar development and surface faceting 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

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

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

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.

Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 10th, 2013 2:00PM