Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
South Rockies.
A Special Public Avalanche Warning applies to this region.
Confidence
High -
Weather Forecast
FRIDAY: Scattered flurries, accumulation 5cm / Moderate to strong west wind / Alpine temperature -8SATURDAY: Mix of sun and cloud / Moderate west wind / Alpine temperature -11SUNDAY: Cloudy with isolated flurries / Moderate west wind / Alpine temperature -7More details can be found on the Mountain Weather Forecast.
Avalanche Summary
On Thursday there was a report of a size 2.5 natural avalanche 50-120cm deep on a NW aspect in Waterton Park. Expect the recent dense storm slab to be reactive to human triggering in the coming days as the all the new snow from the past 10 days starts to settle. Storm slab avalanches have the potential to step down to the basal weakness which would drastically increase the size and destructive potential of a resulting avalanche.
Snowpack Summary
Thursday saw 15-30cm of moist new snow fall on top of the 90cm of low density storm snow that accumulated last weekend. Strong shifting winds have redistributed the previous storm's snow in exposed terrain forming touchy wind slabs. These wind slabs are now obscured by the latest blanket of snow. All this overlies a highly variable old surface which may include wind affected surfaces, facets, and/or a rain crust below around 1500 m. Recent reports suggest a poor bond between the storms' snow and the old surface. In deeper areas, the snowpack appears to be well settled with isolated concerns about the mid-December facet layer which was buried 50-100 cm deep prior to the weekend storm. In shallow snowpack areas and at lower elevations, the snowpack is weak, faceted, and has no structure. Prior to the storm, it was possible to step onto the snow surface in these areas and sink right to the ground.
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.