Watch for fresh slabs building at upper elevations and expect conditions to deteriorate over the weekend. Read more in the latest forecaster blog.
Increasing southwesterly wind will redistribute flurries and loose snow to build new wind slabs and cover older, stiffer slabs. These older wind slab have become increasingly unreactive in the past week, but may still be possible to trigger in steeper more complex terrain features.
50-80 cm of snow sits on a persistent weak layer that was buried near the end of January. This surface hoar/crust interface is slowly gaining strength but may remain human triggerable in steep convex features at treeline and potentially steep alpine features where it presents as a crust.
Light flurries lead us into a bigger storm arriving on Sunday morning.
FRIDAY NIGHT: Cloudy and some isolated flurries, light wind with moderate southwest gusts, treeline temperatures around -8 C.
SATURDAY: Cloudy with isolated flurries and up to 5 cm of snow, moderate west wind, treeline temperatures around -6 C.
SUNDAY: Snow starting midmorning with 10-15 cm of snow by the afternoon, strong southwest wind, freezing level climbing up to 1200 m, treeline temperatures reach -3 C.
MONDAY: Heavy flurries overnight and throughout the day bring 15-30 cm of snow, strong southwest wind, freezing level around 1500 m with treeline temperatures around -1 C.
Minimal avalanche activity has been reported since Monday, with only some small (size 1) wind slabs reactive to skiers on Tuesday and Wednesday.
Wind slab avalanches were much more reactive last weekend, with numerous avalanches on northwest, north, northeast, and east facing features above 1900 m. These avalanches ranged between size 1-2, with 20-50 cm thick slabs triggered naturally, with explosives, and by skiers.
Persistent slab avalanche activity has also quieted down over the past week. In the first 2 weeks of February there were many reports of avalanches triggered by skiers at treeline elevations (1800-2000 m) where a persistent weak layer exists as surface hoar. The drop in activity could be accounted for by subtle factors like diminishing slab properties or possibly by savvy terrain use. Professionals in the region continue to highlight persistent slabs as a lingering concern. There have also been 2 very large explosive triggered avalanches in the Bonningtons in the past month (most recently on Feb 9). These avalanches stepped down to our early December crust layer to produce a 200 cm deep, size 3.5 avalanche.
Flurries over the past few days have given us 10-20 cm of soft snow above old hard surfaces. There may some some new wind slabs on northeast lee features. The most predominant layer underneath the new snow is older wind slabs that formed during a strong northeast wind event last week. Time and warm temperatures are reducing the sensitivity of these older wind slabs to human triggering, but the slabs rest on facets formed during the cold snap, so these wind slabs may persist longer than we're accustomed to.
The upper snowpack continues to settle over another weak layer buried 50-80 cm deep (from January 24). This persistent weak layer may present as facets or a crust. Recent test results show that this weak layer is gaining strength.
We have also been tracking some layers in the mid and lower snowpack including a surface hoar interface buried 70-120 cm deep and a crust from early December that is surrounded by weak faceted grains .These appear to have gone dormant for the time being. A sudden warm up in the form of a Pineapple Express (Atmospheric River), or a large load in a shallow rocky start zone may be able to wake them up.
