Regions
Banff Yoho Kootenay.
With the big high pressure system arriving it will be tempting to start looking at bigger lines. Remember that the structure of the snowpack is so poor that human triggering remains likely. Stick to conservative terrain for the next while.
Weather Forecast
A very strong ridge is moving into the region bringing clear skies and light NW winds on Tuesday. Temperatures will remain cool but the sun effect will be strong. This ridge is expected to remain in place for most of the week.
Snowpack Summary
Sun crusts at lower elevations. Recent wind slabs and cornice growth in the alpine with 30-50 cm of snow in the last week. A 50-100 cm slab overlies the January 6 persistent weak layer of surface hoar, facets and sun crust. Snowpack tests indicate an unstable bond on this layer. The lower snowpack is facetted and quite weak in thin snow pack areas.
Avalanche Summary
A lot of human triggered activity has occurred in the last three days ranging from size 1.5 to size 3! Monday a skier was caught and partially buried in a size 2 slab triggered near Richardson's Ridge at Lake Louise. Flights in the Lake Louise area on Sunday also showed an extensive natural avalanche cycle up to size 3 in the previous 48 hrs.
Confidence
Due to the number and quality 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.