Regions
Banff Yoho Kootenay.
The natural avalanche cycle was tapering off Sunday afternoon. However, it is still primed for human triggering and forecasters expect the danger to return to high with an incoming system starting Monday night.
Weather Forecast
Expect temperatures to rise to slightly above zero at valley bottom on Monday as another moderate system tracks through the forecast region. Temperatures will drop slightly into Tuesday as up to 20cm is deposited by the end of the day. Wind is expected to be moderate from the S/SW throughout Tuesday.
Snowpack Summary
40 - 60 cm of snow since Dec 10 forming a storm slab over facets and surface hoar. New windslabs are common on lee (mostly east) aspects. The lower snowpack is weak and facetted with some avalanches running to ground.
Avalanche Summary
Numerous natural and skier or explosive triggered avalanches over the past few days up to size 2.5 have been reported and observed. Avalanches may run further down slope than expected, so be cautious of overhead hazard.
Confidence
Intensity of incoming weather systems is uncertain on Tuesday
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.