The second avalanche cycle within one week starts on Thursday with large amounts of new snow overlying significant weak layers. Avoid avalanche terrain until the weekend at least and expect road closures - highway avalanche control will be ongoing.
Weather Forecast
The last in a series of westerly storms will cross the region starting overnight on Wednesday and picking up steam through the day on Thursday. Expect 10-15 cm by the end of the day Thursday (25 on the Wapta), and 20-30 cm by Friday morning (up to 50 on the Wapta). Clearing on Friday evening and temperatures dropping to -18 by Saturday.
Snowpack Summary
10-15cm of low density storm snow has fallen in the last 48-hours with the 8-day total reaching 60-80 cm. Add another 20-40 cm by Thursday and we have a significant storm slab development - the snowpack has almost doubled in the last week. The Dec 10 persistent weak layer was found in Crowfoot Glades down 80 cm giving sudden planar test results.
Avalanche Summary
Numerous natural avalanches observed today in the Bow Summit area: size 2.5 natural cornice on Bow Peak; size 2.5 deep slab under the Crowfoot Glacier; size 2.5 natural off Jimmy Junior; size 1.5 skier remote in the Observation Peak trees. This pattern can be expected everywhere in the park right now. Lots of avalanches happening.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.