Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Regions
Purcells.
Tricky conditions with a slowly increasing load over multiple weak layers in the snowpack. Take a conservative approach to your terrain choices.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Saturday: 5-10 cm snow. Light to moderate south-westerly winds. Alpine temperature near -10. Sunday: 5-10 cm snow. Light south-westerly winds. Alpine temperature near -7.Monday: 5 cm snow. Moderate to strong south-westerly winds. Alpine temperature near -1.More information can be found in the Mountain Weather Forecast.
Avalanche Summary
A widespread natural avalanche cycle was observed on Wednesday, with some natural activity continuing on Thursday. Avalanches up to size 4 were reported from all aspects, many failing on persistent weak layers down 1 m or more. Almost all the persistent slabs failed at elevations above 2000 m. The theme on Thursday was still a very touchy snowpack, with numerous large to very large avalanches triggered by explosives.Natural avalanche activity has now slowed, but the potential for human-triggering of surprisingly large avalanches remains elevated.
Snowpack Summary
The current snowpack is complex, with three active weak layers that we are monitoring.60-100 cm recent storm snow overlies a crust and/or surface hoar layer (from mid-January). The crust is reportedly widespread, except for possibly at high elevations on north aspects. The surface hoar is 10 to 30 mm in size and at all elevation bands. The recent snow fell with strong south winds, producing wind slabs and cornices in lee features. Deeper in the snowpack, a persistent weak layer known as the early-January layer is present at all elevation bands, and composed of surface hoar on sheltered slopes and sun crust on steep solar aspects. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs, cracking and avalanches. Another persistent weak layer that was buried mid-December is 60 to 100 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 100 to 150 cm deep and is likely dormant for the time being.
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.
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.