Regions
Banff Yoho Kootenay.
http://www.pc.gc.ca/apps/links/goto_e.asp?destination=Avoid all avalanche terrain including crossing runout zones at valley bottom. Natural activity will likely taper over the next couple of days, but human triggering will be as touchy as it gets.
Weather Forecast
The epic storm has ended and we will see a few "normal" days of weather. -15 to -18C in the alpine Friday with light winds and mainly clear skies and no additional snow.
Snowpack Summary
Thursdays storm dropped 30 - 50cm with variable winds. This combined with other recent snow has overloaded the 3 main mid pack concerns which are the Jan 16th, Jan 6th, and Dec.15 weak layers. These are a mix of facets, crusts and surface hoar and can be found 70cm to over 150cm deep in the snowpack and are currently producing very easy results.
Avalanche Summary
Another widespread cycle Thursday to size 3.5 (what we could see) . These were failing on the above mentioned weak layers. Explosive control was producing size 3 avalanches up to 150cm deep with just the explosive hitting the slope. Most of these avalanches are traveling far into the valley bottom which should be a concern for all users.
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.
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.