Regions
Banff Yoho Kootenay.
Saturday looks like a great day to be out in the mountains, but the avalanche risk is elevated because of Friday's storm. Stick with more conservative terrain choices until better information is known about how the new snow is bonding.
Weather Forecast
A clearing trend is expected on Saturday with light winds and cool temperatures between -10 and -15'C during the day. Sunday will see a 3-5 cm's of new snow, continued light winds and slightly warmer temperatures.
Snowpack Summary
10-20 cm of new snow on Friday with strong W winds has formed wind slabs in lee features down to treeline. The March 15 sun crust is down 30-50 cm on solar aspects and has been sensitive to skier triggering over the last week. The mid- pack and basal layers have been dormant, but shallow facetted snowpack areas are still worth treating cautiously.
Avalanche Summary
Some explosive triggered wind slabs up to size 2 where observed at the local ski areas Friday but observations were limited. Thursday there were a few cornice triggered wind slabs up to size 2 in the Bow Hut area and Sunshine Village. Several skier triggered slides on steep solar aspects have occurred in the past week on the persistent sun crust.
Confidence
Due to the number of field observations
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.
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.