Recent windslabs are becoming the main concern in Little Yoho's fatter snowpack areas. There are however many thinner snowpack areas here where triggering slabs over basal facets are a big concern: Field Ice Climbers beware.
Weather Forecast
Freezing levels are forecast to approach 2200m daily through Monday which may keep slabs sensitive to human triggering. Watch for potential temperature inversions. Moderate to Strong SW winds should start to diminish Saturday and it looks to be cloudy near the divide until Monday when the potential for solar inputs looks likely.
Snowpack Summary
Snowfall since Jan2 has been redistributed by southwest winds yielding extensive wind effect in the alpine. In thick snowpack areas, the Dec 10th weak layer of facets is now down 100-150cm with a stronger snowpack below. In thin snowpack areas, there is little separation between Dec 10 and the weak depth hoar/ facets sitting 40 cm above the ground.
Avalanche Summary
A group just outside of the Lake Louise ski area above the Pika Flats at treeline triggered a sz 2 slab 80cm deep failing 40m wide and running 200m on a SW aspect today. The snow safety team at Sunshine Village saw several windslabs fail in the last 24 hrs one of which scrubbed to the ground and produced a large avalanche off of the Monarch.
Confidence
Freezing levels are uncertain on Saturday
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.