A special public avalanche warning will be issued for the Jasper area this weekend. Avalanche control is planned on the Icefields Parkway on Friday. Expect delays in the afternoon.
Weather Forecast
Freezing levels around 2000 m with no overnight freeze expected Thursday and Friday nights. A brief pulse of precipitation is expected on Friday with temperatures falling with the passage of the front on Saturday afternoon.
Snowpack Summary
There is a wide variation in the snowpack across the forecast region. Continuing moderate to strong SW winds in the Icefields area are forming wind slabs on lee slopes. Last week's snow is now a persistent slab 50-80 cm thick. This slab is sitting over the Jan 29 rain crust on all aspects at treeline and above.
Avalanche Summary
Two size 2 slab avalanches were observed around treeline today on low angle northerly aspects. It is likely that these avalanches failed on a surface hoar layer sitting on the January 30 rain crust.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Friday
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.
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.