With continued reports of remote and rider trigged avalanches on the persistent weak layer, conservative decision making and careful route finding are ESSENTIAL. This layer has been most reactive at the treeline elevation on the BC side, but don’t let your guard down elsewhere.
Though most winds have been light, there have been some localized moderate to strong winds from variable directions (will likely switch to southerly Sunday) . Newer reactive wind slabs will be slow to bond where they sit over cold sugary facets. There is also potential for wind slabs to step down to the late January persistent layer.
Human triggering of this layer is most likely on the BC side of the region, we are still working on figuring out its distribution. Small terrain features are producing small avalanche results, bigger features could produce larger more dangerous avalanches. 40-65 cm snow sits above a buried weak layer of surface hoar, facets, and a crust (depending on elevation and aspect). The surface hoar interface is the biggest repeat offender, and things have been most reactive on northerly and easterly aspects at treeline, but don't let your guard down elsewhere. These kinds of avalanches can happen in surprisingly mellow terrain and be triggered from a distance away.
SATURDAY NIGHT - partly cloudy / light to moderate easterly wind / low -26
SUNDAY - Partly cloudy / light southerly wind / highs of -14
MONDAY - Overcast, trace of new snow / light south west wind / -12
TUESDAY - Partly cloudy, light westerly wind, high of -10
There are recent reports in the South Rockies region of human triggered avalanches on a persistent weak layer of feathery surface hoar. One of the groups made a MIN report for us, check it out. There was also a report of a few natural cornice triggered avalanches in headwall features suspected from the last 36 hours.
Skiers triggered a large (size 2.5) avalanche on a south facing slope in K-Country (forecast region to the north of us) on Thursday. Facets over an old sun crust may have played a role. You can read the MIN report here.
Ski cuts have been producing small avalanches avalanche in reverse loaded terrain.
Variable winds have redistributed loose snow developing slabs in lee and open features. In sheltered zones the surface snow is becoming faceted and sugary.
A persistent weak layer lurks 40-65 cm below the surface. In some places it consists of surface hoar, in other places just facets, or crust/facet combinations. Reports suggest the surface hoar interface at treeline is the biggest repeat offender, and things have been most reactive on northerly and easterly aspects, but don't let your guard down elsewhere.
In most places 30-60 cm loose snow and soft slab overlies a handful of surfaces: wind affected snow at upper elevations and exposed terrain, softer snow in sheltered areas, and a crust on steep, solar slopes and below 1600-1900 m.
A solid mid-pack sits above deeply buried decomposing crust and facet layers near the bottom of the snowpack. Though unreactive under the current conditions, steep rocky slopes and shallow snowpacks should still be approached with caution.
