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Avalanche Forecast

Archived

Mar 9th, 2012–Mar 10th, 2012

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

Regions

Northwest Coastal.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Saturday: 15-25cm of new snow - Strong southerly winds - Freezing level at 600m Sunday: Light snowfall - Light to moderate southerly winds - Freezing level at 400m Monday: Some clearing - Light and variable winds - Freezing level at surface

Avalanche Summary

A few skier-triggered size 1 avalanches were reported on Thursday running on the March 1st surface hoar layer. Storm snow avalanches up to size 3 were reported from the big terrain around Bear Pass. Otherwise, no new avalanches to report. This may speak more to the lack of observations than actual conditions. Expect further avalanche activity with weather forecast for Saturday.

Snowpack Summary

Strong westerly winds are keeping wind slabs fresh and weak on lee aspects. The early February persistent weak layers seem to be bonding, but remain a concern in some parts of the region. Persistent slabs may be reactive to human triggers, particularly below treeline on isolated and sheltered steep terrain where buried surface hoar may be preserved. Surface hoar buried at the beginning of March has also started to become reactive in some areas as the over-riding slab develops. Cornices in the region are reported to be large and unstable.

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.

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.