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Avalanche Forecast

Archived

Nov 27th, 2012–Nov 28th, 2012

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

Regions

Kananaskis.

Sporadic large avalanches have occurred over the past few days including a recent slide on the Rae Glacier. The Nov rain crust will plague us for some time yet. Alpine areas are seeing highly variable wind affect giving some good skiing and some not.

Confidence

Good

Weather Forecast

Winds will shift to the west and continue in the moderate range at ridgetop. A weak system of precipitation is expected to begin early Thursday morning bringing only a few cm's of snow.

Avalanche Summary

A few loose snow slides up to size 1.0 were observed on steep N and E aspects in the alpine. A large slab avalanche on the Rae Glacier appears to have a fracture line of approximately 150cm deep and occurred on a NE aspect at 2700m. This slide failed on glacial ice and ran down to the middle of the glacier.

Snowpack Summary

Several snow profiles today confirmed that the Nov rain crust is alive and well sitting an average of 35cm off the ground. Compression tests were producing results below the rain crust in the moderate range. There is also evidence of on-going wind slab formation in the alpine, but his is not present in all locations. See snow profile from Three Isle Lake.

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.

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.