Regions
Banff Yoho Kootenay.
Natural activity has tapered off, but human triggered avalanches in steep terrain are likely due to the basal weaknesses. This is not the time to venture into big terrain. CJ
Weather Forecast
Mainly sunny conditions with light west winds, no significant precipitation, and alpine temperatures between -3 and -10'C are forecast for the next few days. Freezing level near valley bottom on Monday, rising to 1800m on Tuesday and dropping to valley bottom again on Wednesday.
Snowpack Summary
Widespread wind slabs in lee and cross loaded features at tree line and above. Most windward features are scoured to ground from last weeks wind. Easy, sudden collapse compression test results in the basal depth hoar found at tree line on Hwy 93 N (E side of the highway). Some moist snow on steep solar aspects in the afternoon.
Avalanche Summary
Observed some small solar triggered moist sluffs to size 1, and and one notable size 3 on a S facing alpine feature near Mt. Hector which stepped down to the ground in the last 48hrs. Most natural activity has ceased. Evidence of the widespread cycle from the last week is sobering, with many features failing wall to wall on the basal weak layers.
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.