Regions
Banff Yoho Kootenay.
Rein it in this weekend...Thurs-Fri storm left touchy wind slabs on lee features.AVALANCHE CONTROL planned for Mt. Bosworth, Stephen and Dennis on Saturday. Please no recreational activities
Weather Forecast
Over Friday night temperatures and winds will drop and snow/rain will taper off. Over the weekend, expect cloudy skies, light to moderate ridge wind, and alpine highs in the single digits. No significant flurries for the next several days.
Snowpack Summary
Ongoing storm Friday night is continuing to move the 20-30cm recent snow, forming wind slabs at treeline and above. The moist storm snow and wind slabs overlie weak facets. Below treeline snow was still unaffected by wind on Thursday-Friday, but this could change quickly with Friday nights weather. On Friday there was light rain to 1800 m.
Avalanche Summary
One size 2 observed near Sunshine, N aspect where a thin windslab stepped down to 60-80 cm, propagated 80 m, & ran full path (200 m). Control work on Mt. Bourgeau produced numerous avalanches size 1- 2. One started as a wind slab & entrained all of the facets in the track, hitting the road. This is consistent with other observations this week.
Problems
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.
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.