http://www.pc.gc.ca/apps/links/goto_e.asp?destination=http://www.facebook.com/ParksMountainSafety/posts/768278099888848%E2%80%8ERider loads are still trigging large avalanches on the December 17th surface hoar.
Weather Forecast
An unsettled weather pattern remains over the area today with ongoing flurries amounting to 5cm of snow. Alpine temperatures will peak at -7 with light ridge wind occasionally gusting to strong. A large weather system will start moving over the province late tonight spreading precipitation on Sunday with freezing levels remaining low.
Snowpack Summary
25cm of storm snow now covers recently formed wind slabs in exposed areas. The Dec 17th surface hoar layer is down 60-80cm sitting on top of a thick rain crust facet combo below 2100m and sitting on a settled mid-pack above. This layer is widespread and continues to be reactive to the load of a rider, especially at treeline.
Avalanche Summary
The December 17 surface hoar layer produced a large skier triggered avalanche yesterday on a north aspect at treeline on surface hoar buried 60cm. New snow from the past 48 hours remains powdery in most locations producing small loose avalanches. This storm slab is expected to gain cohesion with forecasted winds and precipitation.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
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.
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.