Regions
Banff Yoho Kootenay.
Natural avalanche activity is tapering with the stable weather pattern. However, we have seen many large avalanches triggered in the last week with minimal inputs. This shows how touchy the current snowpack is. Stick to conservative terrain right now
Weather Forecast
A very strong ridge is moving into the region bringing clear skies and light NW winds. Temperatures will remain cool but the sun effect will be strong. This ridge is expected to remain in place for most of the week. We will see good overnight freezes on Tues and Wed PM with less of a freeze and warmer temperatures on Thursday and Friday.
Snowpack Summary
Sun crusts on solar aspects. 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 which has had lots of avalanche activity on it in the last week. The lower snowpack is facetted and weak in thin snow pack areas.
Avalanche Summary
A size 2.5 avalanche ran on an east aspect alpine feature near Sunshine with the first rays of sun this morning. Otherwise, natural activity is tapering, but conditions remain prime for human triggering. For example, on Monday a skier was caught and partially buried in a size 2 slab triggered on a west aspect of Richardson's Ridge at Lake Louise.
Confidence
Freezing levels are uncertain on Friday
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.