Regions
Banff Yoho Kootenay.
Although natural avalanche activity will taper, avalanche control on Jan. 7th produced size 2 (deep enough to bury a human) or greater avalanches on most if not all shots. Now is the time for caution!
Weather Forecast
NW flow continues but with a break in the weather systems for Thursday. Expect clearing skies and temperatures falling to between -10 and -15 and falling winds. Friday the temperatures will warm back up again, with the possibility of light precipitation.
Snowpack Summary
Moderate SW winds and warm temperatures today created windslabs at alpine and treeline elevations. These windslabs bond poorly to the Dec 18 layer of facets, crust and some surface hoar down 20-40 cm. At the bottom of the snowpack, the deep peristent basal problem is still a concern and was triggered using explosives today.
Avalanche Summary
Avalanche control in Kootenay and Yoho Park produced between 10-15 avalanches between size 2 and 3. Mostly size 2's with a couple of larger ones. Human triggering is very likely at this time.
Confidence
Due to the number and quality of field observations
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.