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Avalanche Forecast

Archived

Jan 15th, 2013–Jan 16th, 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 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.

Regions

Banff Yoho Kootenay.

Alpine lee areas are becoming loaded from recent strong wind. A small avalanche cycle has subsequently ensued. See photo of preserved surface hoar (Jan 6 layer).  en francais

Weather Forecast

Warm temps and strong winds from the NW will increase the danger rating to considerable tomorrow. The winds will subside and then pick up again on Thursday. However, at this time much of the snow will have already been transported.

Snowpack Summary

30 to 50cm of snow sit over the Jan 6th interface. Today, in Kootenay, the Jan 6 interface was well preserved surface hoar between 3 to 5mm in size. Snowpack tests provided easy shears. The slab characteristics were 'sudden planar', or rather, the column popped out like a cash register drawer. No other significant shears were noted.

Avalanche Summary

Several avalanches were observed in the alpine from recent wind loading from the NW. These observations included Mt. Hector, Observation Peak as well as other locations. The avalanches were between size 1.5 and 2.

Confidence

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.