Regions
Banff Yoho Kootenay.
Increased wind loading due to light precipitation and moderate to strong W winds is the main thing to watch over the next several days. Ice climbers in particular should be aware of possible changing conditions high above them. CJ
Weather Forecast
Cloudy weather with light precipitation and moderate to strong W winds at ridge tops are forecast for the next several days. Temperatures should remain between -6 and -14'C. 5-10cm of new snow is expected on Monday and Tuesday.
Snowpack Summary
10-20cm of recent storm snow sits on the early December facets. Strong W winds are creating wind slabs on lee aspects at tree line and in the alpine. The mid pack is mainly facets but still dense enough to support the weight of a skier in many areas. In alpine areas the October melt freeze crust is present near the base of the snow pack.
Avalanche Summary
A couple of wind triggered natural avalanches up to size 2 have been reported out of lee aspects on steep alpine terrain in the last 48hrs with one close call reported on Polar Circus on Cirrus Mountain. With the mild temperatures cornices are forming and are quite delicate at this time.
Confidence
Intensity of incoming weather systems is uncertain
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.