Regions
Banff Yoho Kootenay.
The Feb 10th layer is persistent and remains a significant concern in the snowpack. Enjoy the great ski conditions but stick to moderate terrain and don't let the clear skies lure you into bigger lines until the conditions improve. CJ
Weather Forecast
Alpine temperatures down to -15'C tonight then warming to -8'C Tuesday. A warming trend is expected for Wednesday and Thursday with alpine temperatures between -10'C and 0'C. Continued clear skies, light Northerly winds and no new precipitation is expected for the next three days.
Snowpack Summary
25-60cm of recent storm snow is sitting over the Feb10th layer of facets, sun crust and surface hoar. Field tests continue to show an easy to moderate sudden collapse at this interface. Some isolated wind slabs are present in the alpine. If triggered these wind slabs could step down to the Feb 10th interface.
Avalanche Summary
The natural avalanche cycle has subsided but skier triggered slabs remain likely. A skier triggered (Class 1) from yesterday was observed at treeline on the exit out of Purple Bowl in the Lake Louise area. We have also had other skier triggered, skier remote, and natural avalanches up to Class 2 in the last 72 hours on the Feb 10th interface.
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.