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Avalanche Forecast

Archived

Dec 8th, 2012–Dec 9th, 2012

Alpine
Natural avalanches possible, human triggered probable.
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

South Rockies.

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Sunday: A short lived period of high pressure exists into midday Sunday. In the afternoon a weak upper trough approaches bringing cloudy skies, cooler temperatures, and moderate-strong West winds. Snow amounts 5-10 cm, alpine temps near -9, freezing levels at valley bottom.Monday: Trace of new snow, ridgetop winds NW 40-60 km/hr, alpine temps near -9, freezing levels valley bottom.Tuesday: Moderate snow fall amounts, ridgetop winds SW 30 km/hr, alpine temps near -8, freezing levels 1100 m in the afternoon falling to valley bottom overnight.

Avalanche Summary

No recent avalanche observations.

Snowpack Summary

Recent storm accumulations have been variable throughout the region, however some ares saw significant snowfall earlier in the week. Recent accumulations may sit over a rain crust that extends up to 2000 m, the new snow may have a poor bond to this crust. Widespread wind slabs exist at higher elevations, although I suspect that in recent days they may have gained some strength. There have been reports of buried surface hoar up to a metre down. This layer, which was buried at the end of November, seems most prevalent on the west side of the region. Little is known about its current reactivity.At the base of the snowpack an early November crust which is associated with a layer of facets either directly above or below. Recent tests have shown sudden results at this interface. In general, snowpack data is sparse in this region and significant variations likely exist from one drainage to another. Digging down and making your own observations will be critical to safe slope selection. Any observations from the field are welcome at [email protected].

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.