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Avalanche Forecast

Archived

Nov 21st, 2011–Nov 22nd, 2011

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Northwest Coastal.

This bulletin is based on limited data. Local variation in conditions and danger levels are likely to exist. To produce more accurate forecasts, we need information. Please send an email to [email protected]

Confidence

Fair - Due to limited field observationsfor the entire period

Weather Forecast

Tuesday: Expect another 30-40cm, especially in southern coastal areas, with freezing levels as high as 700m and strong southwesterly winds.Wednesday: Continued moderate snowfall in southern coastal areas with another 30-40cm possible. Freezing levels back down to valley bottoms and strong southwesterly winds.Thursday: Another pulse of moderate snowfall is expected.

Avalanche Summary

No recent avalanche have been reported, but I suspect natural avalanche activity occurred in response to recent heavy loading from snow and especially wind. I expect natrual avalanche activity to continue as long as it's snowing asn blowing, and the potential for human-triggering to remain for the forecast period.

Snowpack Summary

As of Monday afternoon, recent storm snow totals were in the 30-60cm range. Varying temperature, precipitation intensity, and wind throughout the recent storm, as well as surface hoar on the previous snow surface, has probably resulted in various weaknesses within and under the recent storm snow. Previous storm snow weaknesses could also be lurking in the upper snowpack. The mid and lower snowpack is generally well settled and strong with an old rain crust near the ground.

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.