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Archived

Avalanche Forecast

Dec 1st, 2012–Dec 2nd, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Coast.

Limited field observations and reports exist from this region. Conditions may be variable. It is important to be familiar with the snowpack and avalanche problems that may exist in your local mountains.

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

The recent weather pattern continues, with a very persistent deep low off the coast driving a moist, mild SW flow over the region. Moderate accumulations are expected through the forecast period, accompanied by moderate S-SW winds. Sunday: Fzlvl’s 1300 m, snow amounts near 5 cm, ridgetop winds S 20-30 km/hr, alpine temps -4.Monday: Fzlvl’s 1200 m, snow amounts 8-15 cm, ridgetop winds S 35 km/hr, alpine temps -4.Tuesday: Fzlvl’s 1300 m in the am then falling to 700 m in the afternoon, snow amounts up to 20 cm, ridgetop winds S 30 km/hr, alpine temps -5 falling to -8.

Avalanche Summary

No new avalanche observations have been reported.

Snowpack Summary

Continued pulses of light-moderate snow accumulations, and strong ridgetop winds. Storm slabs and new wind slabs will load a variety of weak surfaces. These surfaces consist of large surface hoar, a thin sun crust, surface facets. The new snow may have a poor bond to these underlying weaknesses. Below the surface, the mid-pack seems to be settled and bridging over the early Nov facet/crust. However, near the bottom of the snowpack under the crust exists large, low density faceted crystals.Snowpack tests from earlier this week showed sudden collapse ("drops") results on the early November facet/crust deep persistent weakness. Because this weakness is so close to the ground in most areas, associated avalanche activity will likely be limited to slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, glaciers, etc.). Be aware of triggering this layer from thin, rocky areas, this persistent weakness my be a low probability/ high consequence scenario.Below treeline the snowpack generally sits below threshold.

Avalanche Problems

Storm Slabs

Storm slabs and wind slabs are overlying a variety of weak surfaces. If there is a poor bond, natural activity is to be expected. Rider triggers are likely; especially on wind loaded lee slopes.
Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Heads up, freshly wind loaded features may be easily triggered>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

Typical trigger points include shallow variable snowpack depths, and thin rocky areas. Difficult to trigger, but often result in very large and destructive avalanches. Suspect terrain: offers a smooth ground cover (scree, grassy, rock slabs etc.)
Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 6