Regions
Banff Yoho Kootenay.
The weather is finally changing this week. Not much snow is expected, but the winds are forecast to be West, 50-70 km/hr in alpine areas on Tuesday. Heads-up for resulting windslabs up to size 2. A subtle change from the conditions of the past weeks.
Weather Forecast
The good news it that this strong ridge of high pressure is retreating, and this week we return to a more typical westerly flow which aligns the storm track over our area. The bad news is there's not much snow in the that flow. Expect overcast skies and trace amounts of snow for Tuesday along with moderate SW winds up high and temps from -5 to -10.
Snowpack Summary
The snowpack has been static now for weeks, with little change other than the slow, ongoing process of facetting. Over time, this results in a gradual weakening of the snowpack beginning in shallow areas and the top 20cm of the snowpack. This is of little consequence until the next storm, when new snow will probably bond poorly these weak facets.
Avalanche Summary
On Sunday in Kootenay National Park, ski tourers triggered two size 1.5 slab avalanches near to Vermillion Peak. Reports indicate these were windslabs resulting from the recent 10 cm of snow and wind, bonding poorly to a sun crust at 2500 meters.
Problems
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.