Regions
Northwest Inland.
Storm slabs continue to develop with each pulse of new snow and wind.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Overnight: Freezing level down to valley bottoms, 2-3 cm of new snow, moderate southwest winds. Thursday: Daytime freezing level around 700 metres, 3-5 cm of new snow, moderate southwest winds, and a chance of sunny periods in the afternoon. Friday: Daytime freezing level around 500 metres, 2-3 cm of new snow, moderate southwest winds. Saturday: Daytime freezing level around 500 metres, 3-5 cm of new snow, moderate southwest winds.
Avalanche Summary
Numerous natural avalanches up to size 2.5 were reported from the west of the region in the Howson's on Tuesday. Natural avalanches up to size 2.0 were reported from the Hankin area on Monday.
Snowpack Summary
Storm slabs continue to build with each pulse of snow and wind. Warm temperatures will make touchy slabs at higher elevations and unstable wet snow at lower elevations. A weak interface that was buried in late February may finally have enough snow above it to form a reactive slab. The interface is composed of facets, crusts, and surface hoar and may be 40-60 cm deep. There's uncertainty about the distribution and reactivity of this interface. The mid-pack is well consolidated and sits above weak sugary snow near the ground. The deeper basal weakness remains a concern in thin rocky start zones and shallow snowpack locations.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.