Regions
Banff Yoho Kootenay.
Ice climbers should be very cautious in steep gullies. Strong/extreme winds have loaded start zones and have formed touchy wind-labs.
Weather Forecast
Continued strong to extreme wind is expected near 3000m until Monday morning. Up to 15cm of new snow is also expected. Beyond Monday we expect to see a cooling trend accompanied by clear weather.
Snowpack Summary
Small amounts of new snow continues to be transported into lee areas by strong to extreme wind - particularly near Lake Louise and on the E side of Hwy 93N. Near the divide, deeper snow-packs are stronger and more supportive. Surface hoar up to 10mm was buried by a trace in some areas and blown away in others by strong W winds Saturday and Sunday.
Avalanche Summary
Although reported from the Jasper forecast region a very close call was observed yesterday on the ice climb 'Polar Circus'. Two ice climbers narrowly missed being hit by a large avalanche that went right over their heads. It was suspected to be size 2.5. The high winds in the area likely was the cause for the slide.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Monday
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.