Regions
Banff Yoho Kootenay.
A big winter storm is approaching and conditions will change starting Wednesday. Potentially 30-50 cm of new snow plus strong winds by Thursday. Modify your plans accordingly and avoid exposure to avalanche terrain for the next several days.
Weather Forecast
A significant storm enters the region starting at midnight on Wednesday and continues through Thursday night; it will be a snowy few days. There is much uncertainty in the models, but some are predicting up to 30cm on Wednesday and another 20cm on Thursday - most of this is expected at Lake Louise and north, accompanied by strong westerly winds.
Snowpack Summary
Storm and windslabs will develop on the snow surface starting Wednesday and continue to build through the storm with 30-50 cm in the forecast. These slabs overlie 50-70 cm of weak facets with a melt-freeze crust in the middle (Oct. 26 crust). Overall the snowpack is weak due to its early season nature and could become overloaded by this storm.
Avalanche Summary
No new avalanches observed today on the Banff-Jasper highway area or on Observation Sub-Peak. Both Sunshine Village and Lake Louise ski patrols reported no significant new avalanches today - but we are all anticipating the next 24-48 hours to see how much new snow will result from the storm.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Wednesday
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.