Regions
Banff Yoho Kootenay.
Heading into the weekend, the unstable snowpack compounds on Friday with more snow, increasing winds and a sharp rise in temperature - all three of the big factors. We expect an avalanche cycle on Friday. Watch your exposure carefully, its tricky.
Weather Forecast
A westerly flow brings another system across the region starting Thursday evening and running until Saturday morning. Friday will be a stormy day; expect another 10 cm at treeline with temperatures rising 10-15 degrees through the day. Winds will also rise, reaching SW 50-75 km/hr at 3000m throughout Friday morning.
Snowpack Summary
50-60cm of storm snow over the past week has been surprisingly reactive. With the addition of more snow on Friday, increasing winds and rising temperatures, the upper meter of the snowpack will continue to produce avalanches on Friday and Saturday. Warming and additional loading may even re-awaken the weak, facetted base which underlies everything.
Avalanche Summary
Large avalanches continue to occur daily.. On the east side of Hwy93N we triggered a size 3 on Mt Hector and a size 2.5 on Dolomite Peak from avalanche control on Thursday - both released in the deep facets. Also a size 3 on Mt Field. Observed numerous recent (last 48 hr) avalanches including several fresh size 2-2.5's above the Dolomite Peak loop.
Confidence
Forecast snowfall amounts are uncertain on Friday
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.
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.