Mild temperatures, rain and strong winds are decreasing the snowpack stability. Several large avalanches from treeline and below occurred on Tuesday near the Columbia Icefields.
Weather Forecast
Cooling temperatures over the next 48 hours with the chance of snow flurries. The SW flow will become more westerly with the freezing levels dropping to the valley bottom overnight and not reaching the treeline during the day. Cooler temperatures are forecast for the Icefields area where the greater amounts of snow can also be expected at elevation
Snowpack Summary
At treeline and below warming temperatures and rain has increasing the temperature of the snowpack. Moist snow in the upper pack can be anticipated. Surface crusts will form when temps drop. Solar facing slopes close to treeline may have buried crusts with slab snow above. Deeply buried weaknesses near ground. Windslabs in the alpine.
Avalanche Summary
Slab and point release avalanches observed Tuesday up to size 2.5 from treeline and below. All events are stepping to ground. Most are being triggered by warm temperatures and rain. One or two of these events started above treeline in areas where strong and extreme winds, from the SW, are developing wind slabs. These to are steeping down to ground.
Confidence
Freezing levels are uncertain on Wednesday
Problems
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
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.