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Avalanche Forecast

Archived

Dec 9th, 2013–Dec 10th, 2013

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Purcells.

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

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.