Regions
Banff Yoho Kootenay.
Strong winds are expected Sunday morning. Give overhead avalanche terrain a wide berth until winds settle back down later in day.
Weather Forecast
Freezing levels Saturday reached 2300m with moderate West winds. Overnight, alpine winds are forecast to increase to strong to extreme as a cold front passes bringing some precip and a cooling trend begins. Midday Sunday should bring and end to the winds as temperatures drop further. Clearing overnight into Monday.
Snowpack Summary
10-20cm of snow over the last week over isolated suncrusts and surface hoar. Widespread wind effect in the alpine creeping into treeline with current winds. Of greatest concern are the weak facets and depth hoar at the base of the snowpack. In thinner snowpack areas with less than 150 cm of snow, triggering a slab on these facets is more likely.
Avalanche Summary
No new avalanches observed or reported today.
Confidence
Wind speed and direction is uncertain on Sunday
Problems
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.
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.