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Avalanche Forecast

Archived

Dec 4th, 2014–Dec 5th, 2014

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

Regions

South Columbia.

I'd veer away from thin snowpack areas, rocky outcrops and large steep alpine slopes which didn't avalanche last week.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Warm air from the Pacific will push in, bringing warming temperatures but not much precipitation in the short term.Friday: Light snow. Remaining cool. Light to moderate SW winds.Saturday: Light snow. Moderate to strong SW winds. A layer of warm air may form at mountain height, while the valleys remain cool.Sunday: Light snow. Light winds. Temperatures may start to rise towards -2 at treeline.

Avalanche Summary

Explosives testing to the north of the region on Wednesday resulted in isolated soft slabs on a layer of surface hoar and facets at alpine and treeline elevations. Otherwise, no new avalanches have been reported. There is still a chance of triggering avalanches on persistent weak layers formed during November, with high consequences.

Snowpack Summary

Surface: Before Friday, snow surfaces included wind slabs (variable in distribution); surface hoar, which has grown large in sheltered spots; and sun crusts on steep south-facing slopes.Upper-mid pack: Anywhere from 5-30 cm of settling snow sits on a crust which formed in late November. This crust is supportive above about 1800m, but is breaking down at lower elevations. About 1m down, a weak layer of surface hoar and/or facets can be found in some locations. Snowpack tests on this layer are showing improving results, but in some locations "pops and drops" indicate this beast could still be touchy.Lower pack: A thick rain crust from early November is buried over a metre down.

Problems

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.