Regions
Banff Yoho Kootenay.
High freezing levels & precipitation with strong winds aloft are telltale signs that avalanche terrain is best avoided this weekend until the storm ends and temperatures cool things off. Avoid any avalanche terrain and make simple terrain choices. PJ
Weather Forecast
The Jet Stream is lined up in a north westerly flow on the east side of the Divide coupled with strong SW flow from the southern Pacific providing a positive moisture feed until Saturday afternoon with light snow through Sunday. The winds aloft will remain strong until Saturday evening. A break in the weather is expected by Monday morning.
Snowpack Summary
45 - 70 cm of recent storm overlies a crust from January 30th. The recent heavy precipitation, wind and warmer temperatures have created storm slabs which will put an enormous amount of stress on the January 30th crust interface. The basal facets from Nov 6th could reemerge in step down events with this huge stress to the snowpack.
Avalanche Summary
One natural size 2.5 avalanche narrowly missed a number of snow-shoers today in Lake O'Hara out the Schaeffer Bowl area. Several large avalanches up to size 3 were observed on the Highway 93S. Poor weather and embedded fog limited the forecaster's observations today but there were undoubtedly many more avalanches occurring than were seen today.
Confidence
Forecast snowfall amounts are uncertain on Saturday
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.