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Avalanche Forecast

Archived

Mar 16th, 2012–Mar 17th, 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 possible, human triggered probable.

Regions

Purcells.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Unsettled conditions are expected for Saturday and Sunday. Light winds and convective snow showers are forecast to bring up to 10 cm on Saturday. Clearing overnight should turn to broken skies during the day on Sunday. There may be some clearing on Monday if a ridge of high pressure extends far enough north. If the ridge does not go far enough north, then expect cloud and scattered flurries to move in from the northwest.

Avalanche Summary

Natural avalanches up to size 2.0 and explosive controlled avalanches up to size 2.5 were reported from the Dogtooth on Friday. Avalanches were confined to the 40 cm of new snow. Reports confirm that there was a widespread cycle to size 3.0 in the past 48 hours. A skier remotely triggered a size 3.0 avalanche from about 50 metres away on Wednesday in Canyon Creek. The slide was reported to be from a west aspect below treeline at about 2000 metres. Expect natural and easily triggered avalanches to continue. If the sun comes out, expect natural activity in the storm slab that may step down to the PWL once it is in motion.

Snowpack Summary

40 cm of new snow overnight with light-moderate southerly winds created an unconsolidated slab above the recent storm snow. The combined slab above the mid-february persistent weak layer is now between 150-200 cm. Some operators continue to get easy-moderate sudden planar character shears on the mid-february surface hoar in shallow areas. The persistent weak layer continues to be a concern at all elevations, and may show wide propagations on low angle terrain below treeline. The new snow may consolidate and release naturally if the skies clear and we get some strong solar radiation. Snowpack conditions continue to be tricky to evaluate, and are variable throughout the region.

Problems

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.

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.