Regions
Banff Yoho Kootenay.
Danger rating based on the highest rating of the day in relation to temperatures, and we expect an avy cycle on Thursday. Avalanche control on Mt. Whymper, Simpson, Vermillion, Wardle, and Mt. Bourgeau Thursday. No activities in these locations.
Weather Forecast
Mainly sunny conditions Thursday will see lots of solar input which will finally bring some spring temperatures to the region. Light winds and no snow in the forecast. Next week looks like a very warm week which will bring a dramatic spike in the avalanche danger. Stay tuned.
Snowpack Summary
Up to 50 cm of storm snow near the divide affected by strong SW winds Tuesday evening. Several buried temperature crusts exist to 2000m on all aspects and to ridge tops on solar slopes, including the Mar 15 sun crust down 35-50 cm in the alpine. Moist snow at lower elevations, with the entire snowpack becoming moist near valley bottom.
Avalanche Summary
Some size 2 wind slabs reported at sunshine with explosives. Avalanche control on Mt. Bosworth Wednesday produced avalanches to size 3 with good propagations up to 200m wide, and further West a size 3.5 out of Emerald Lake slidepath occurred last evening.
Confidence
Freezing levels are uncertain on Thursday
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.
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.