Current conditions are complex and very uncertain. A big-picture approach using avoidance of terrain features with wide margins is necessary.
Human-triggered avalanches are likely in any avalanche terrain where a slab sits over the deeper facet layers. Be watchful for remote triggers from greater than anticipated distances.
Trying to outsmart this condition will likely not end well. Backcountry users need to maintain discipline for the coming weeks and perhaps months.
Slabs typically 25-60cm thick sit over a Dec. 17 weak layer of facets that was on the surface during the prolonged deep freeze. If initiated, the big concern is that it can step down to the deeper weak layers resulting in large avalanches. Below treeline the problem exists anywhere there is a slab overlying the deeper weak layers.
Much of the bottom half of the snowpack is very weak and faceted. Avalanches have been occurring on this layer, or starting higher in the snowpack and "stepping down" to the basal facets causing large avalanches. Anywhere a slab is present over the basal facets we expect human triggering to be likely and remote triggering to be possible.
A skier-triggered size 2 avalanche in the Emerald Lake slide path occurred Saturday on the basal facets resulting in life-threatening injuries.
Mostly size 1 results from control at local ski areas. A flight today in the Lake Louise area showed avalanches up to size 3 but likely 48+ old. Extensive whumping and remote triggers of very small features below tree-line in Little Yoho today.
10-20 cm of soft surface snow in sheltered areas. Below this a settled slab 25-60 cm thick sits over a weak layer of facets and surface hoar from Dec 17. Below this another 20-40 cm of facets sit over the weak Nov 16 interface, with the bottom 20-50 cm of the snowpack made up of weak facets and depth hoar. Total snowpack depths of 80-140 cm at treeline.
Warmer than seasonal temperatures (close to zero in the valley and -5 at the ridge) is expected Monday and Tuesday. Wind speed is a bit uncertain but ranges from light to moderate from the NW. With the warm temps come clearing into Monday with no precipitation.
