Regions
Banff Yoho Kootenay.
Conditions are improving after Thursdays monsoon, but there is still uncertainty around the persistent slabs and how reactive they are, especially above 2500m where the rain line ended. SH
Weather Forecast
Another 5 cm possible on along the divide on Saturday with lesser amounts on the Eastern slopes. Winds will be in the moderate range from the SW and temperatures will go above zero in Banff and stay just below freezing further into the mountains. On Sunday another 5-10cm is expected with increasing winds.
Snowpack Summary
There is up to 75 cm new in the alpine from the last week with specific wind slab development on lee aspects. Below approx. 2600 there is a new Nov.23 rain crust forming from the torrential rains Thurs. The concern before the storm was the Halloween crust and/or facets near the bottom of the snowpack,which may now be of most concern in the alpine.
Avalanche Summary
Activity has slowed dramatically after the big rain event Thursday which saw natural and man made avalanches up to size 3 which were a combination of persistent slabs and loose wet avalanches. Lake Louise ski hill was reporting some explosive controlled persistent slab results to size 2 today in alpine features.
Confidence
Due to the number and quality of field observations
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.