Regions
Banff Yoho Kootenay.
A brief reprieve from storm systems, but the next one on Wednesday looks warm. Enjoy the good snow for one more day, but be careful as the Halloween crust/ facet layer is spooky!
Weather Forecast
Tuesday is a rest between storms with light winds, cool temps and precip starting in the afternoon (10 cm overnight). Wednesday is looking to be quite warm with freezing levels rising to ~ 2500m and rain at lower elevations. Temps will cool on Thursday with freezing levels dropping to ~ 2000m and 20- 30 cm of snow.
Snowpack Summary
30 - 70 cms of new snow over the last 5 days has been blown into windslabs up to 1 meter deep in the alpine. Where windslabs don't exist, this snow has formed a 30-60 cm slab that sits on the Halloween crust/facet interface. This interface is a crust below ~ 2400m on polar aspects and higher on solar aspects. Total snowpack at treeline is 80-100 cm
Avalanche Summary
Lots of avalanche activity on Monday. Some examples: -Widespread natural activity up to size 2.5 on the National Geographics and Whitehorn gullies in the Lake Louise ski hill and backcountry-A size 3 on a NE aspect of Pilot mountain with a ~ 500m fracture line. Many of the avalanches initiated in the low alpine where the halloween crust exists
Confidence
Due to the number of field observations on Monday
Problems
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.
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.