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Avalanche Forecast

Archived

Mar 5th, 2014–Mar 6th, 2014

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

Regions

South Rockies.

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The second in a pair of fronts will cross the region tonight or early Thursday before conditions become drier into the weekend.Tonight and Thursday: Periods of snow (up to 15cm) / Winds: moderate southwesterly gusting to strong / Freezing level: 1600mFriday: Sunny periods / Winds: moderate southwesterly / Freezing level: 1600mSaturday: Cloudy / Winds: moderate southwesterly / Freezing level: 1500m

Avalanche Summary

On Tuesday, we received a report of a natural storm slab avalanche and multiple human-triggered storm slab avalanches up to size 2 releasing down as deep as 35cm.

Snowpack Summary

30-45cm of new snow now overlies an old surface of surface hoar, a sun crust, and/or facets. Recent moderate to strong SW winds have created wind slabs in leeward and cross-loaded features. The midpack is broken by a persistent weak layer consisting of a crust, facets, and/or surface hoar that was buried mid February. In the thinner snowpack areas such as the Crowsnest and northern Elk Valley the layer can be found buried between 60 and 90 cm. In thicker areas such as the Flathead and around Fernie it may be found as deep as 150cm. This layer continues to show a high degree of sensitivity to human triggers especially in where it is buried closer to the surface. Check out the South Rockies Blog for a video discussing the persistent weak layer and the current avalanche problem. A weakness at the base of the snowpack may still exist in isolated areas of the region but triggering this layer is unlikely.

Problems

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.