Avalanche Forecast

Archived

Mar 17th, 2013–Mar 18th, 2013

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 possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis.

Up to 40cm of recent snow at treeline and above. Winds have been variable so storm slabs are being found on all aspects. Winds will increase. Westerly winds will become strong on Monday so watch for these new slabs to become more reactive.

Confidence

Good

Weather Forecast

An additional 5cm of new snow will likely fall before Monday morning as the cold air continues to push into the forecast area. Winds on Monday are expected to increase into the moderate range at higher elevations out of the NW and temperatures are forecast to cool down into the -18C range in the Alpine. Freezing levels will remain at the valley bottoms. Winds will be a key factor to pay close attention to as lots of recent storm snow is now available for transport.

Avalanche Summary

A few sz 2 natural avalanches were observed on solar aspects at treeline and above over the past 24hrs. These slides appear to have failed on the 0312crust. Also, lots of loose dry slides were observed in steep alpine terrain on all aspects.

Snowpack Summary

Up to 35cm HN24 at treeline tapering down to 20cm at valley floors. This snow was rapidly settling at lower elevations due to the warm temps. Variable light (gusty to moderate) winds were creating pockets of touchy storm slabs along ridgelines lines at treeline and in open features in Alpine terrain. There was also reverse loading on-going at higher elevations due to the NW winds. The 0312 crust was found down 85cm on a south aspect at treeline and the 0303 crust was found down 110cm (Photo). Easy shears can be found in the upper snowpack within the storm snow and moderate to hard sheers persist down 85 on the 0312 crust. The 0312 crust is supportive at lower elevations which makes travel easy. Beneath this crust the snow is moist.

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.

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.