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Avalanche Forecast

Archived

Feb 15th, 2016–Feb 16th, 2016

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

Banff Yoho Kootenay.

We have a classic Rockies snowpack with persistent weak layers right now and numerous close calls over the last week prove this. Have patience and stick to conservative terrain for a while until the snowpack settles out!

Weather Forecast

The jet stream is over us so expect to get regular snow throughout the week. We should get 5-10 cms Monday night with a clearing trend Tuesday. The next storm will come in on Wed around noon and we should see 5-10 cms into Thursday. Freezing levels will remain around 1200m with a slight warming trend on Wed. Alpine winds will be moderate W/SW.

Snowpack Summary

Fresh windslabs and cornice growth in the alpine with 15 to 30 cm of recent snow and west winds. A 50-100 cm slab overlies the January 6th weak layer of surface hoar, facets and sun crust and snowpack tests indicate an unstable bond between the two. The lower snowpack is facetted and quite weak in thinner areas (<1.5m) and settled in thicker areas.

Avalanche Summary

Close calls continue - on Monday the 15th, two climbers triggered a size 2 slab on the approach to "Nightmare on Wolf Street" on the Stanley Headwall. This failed on the ground and would have been an ugly ride. Last Friday, a group of 8 triggered a size 2 just left of the regular final approach slope to Bow Hut

Confidence

Due to the number of field observations

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.