Regions
Banff Yoho Kootenay.
Another storm will reach the area Sunday afternoon. Caution is recommended at treeline and above as this new load tests the persistent weak layer.
Weather Forecast
Another system is forecast to arrive Sunday afternoon. The pattern of this storm will be much the same as the last however freezing levels look to be much lower at around 2000m. We expect up to 20mm to arrive with moderate SW winds as first the warm front passes followed by a cold front at around 9 pm. Further precip is expected through Tuesday.
Snowpack Summary
In the Alpine there has been significant amounts of both snow and wind in the last two weeks. Significant amounts of Precip came as rain below about 2500m on Thursday creating a new crust that has 5 to 10 cm over it. The main concern in the snowpack remains the weak facets associated with the Halloween crust in the mid to lower snowpack.
Avalanche Summary
Although natural avalanche activity has slowed with more settled weather in the last few days a few have been reported on the crust and facets at around the 2500m range to sz 2.5. A significant cornice failure was also reported by Sunshine Village. Explosive control continues to produce results on the facets /crust as well as a few wind slabs.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Sunday
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.