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Avalanche Forecast

Archived

Nov 23rd, 2011–Nov 24th, 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.

Avalanche danger is expected to remain HIGH as long as the intense storms continue.

Confidence

Poor - Due to limited field observationsfor the entire period

Weather Forecast

Thursday: 20-30cm of snow with freezing levels as high as 900m and extreme southerly winds becoming westerly late in the day.Friday: Light to moderate precipitation increasing intensity throughout the day with 10-20cm expected by the evening. Strong westerly winds becoming extreme southerlies. Freezing levels in valley bottoms in the morning rising to 900m throughout the day.Saturday: Heavy precipitation, extreme southwesterly winds and freezing levels as high as 1000m

Avalanche Summary

No recent avalanche have been reported, but I suspect natural avalanche activity occurred and will continue in response to heavy loading from snow and especially wind.

Snowpack Summary

Another 15cm last night keeps adding to the recent storm snow total, which is now probably 70-80cm since the weekend in some areas . Varying temperature, precipitation intensity, and wind throughout the recent storms, as well as surface hoar on the previous snow surface, has probably resulted in various weaknesses within 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.