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Avalanche Forecast

Archived

Dec 4th, 2011–Dec 5th, 2011

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

Regions

Northwest Inland.

Confidence

Poor - Due to limited field observations

Weather Forecast

A radical above freezing layer is forecasted for Sunday night into Monday. Freezing levels as high as 2800m are possible. A cold front sweeps across the NW coast bringing as much as 30mm to the more coastal locations Monday afternoon as ridgetop winds build to 80 - 95 km/h out of the W. Freezing levels lower Monday as the cold front moves inland.Cold post frontal air keeps the region dry & cool on Tuesday. Ridge of high pressure rebuilds Wednesday & Thursday with an outflow pattern. Another above freezing layer is forecasted for later in the week.

Avalanche Summary

Natural and explosive controlled avalanches up to size 4.0 releasing in the storm snow. Some of the larger releases have been from glide avalanches. Most of this activity is in the West of the region closer to the coast. We don't have any new reports from the Interior.

Snowpack Summary

Very strong W-SW winds have probably wreaked havoc in any exposed terrain. Expect to find scoured areas, sastrugi, and hard or stiff wind slabs. The average snowpack depth at treeline is over 200cm. The mid and lower snowpack are generally quite strong. Watch for clues of instability like whumpfs or shooting cracks, and if observed back off any steeper objectives.

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.