Large human triggered avalanches are likely this weekend, particularly on slopes above 1600 m. Conservative terrain choices are critical right now. The persistent weak layer of surface hoar will be slow to gain strength.
New snow combined with moderate to strong northwest wind is creating touchy wind slabs in lee terrain features. These wind slabs may be sitting on top of weak surface hoar crystals in lower alpine and treeline areas, which would make them more easy to trigger.
A surface hoar layer buried near the end of January is now down 40 to 80 cm and has recently been quite sensitive to triggering. This layer has been the most sensitive right at treeline, but it is thought to extend into the alpine too.
There is a deeper surface hoar layer down 60 to 100 cm in the northern part of the region around Pine Pass which may also remain sensitive to human triggering..
Brrrr! Arctic air ushers in bitterly cold temperatures with no new snow in sight.
FRIDAY NIGHT: Freezing level at valley bottom, overnight low temperature bottoming out around -25 C, moderate to strong northwest wind, no significant snowfall expected.
SATURDAY: Scattered cloud cover, daytime high temperature around - 10 C, light to moderate northwest wind, trace of snow possible.
SUNDAY: A few clouds, daytime high temperature around -15 C, light to moderate north/northwest wind, no snow expected.
MONDAY: Scattered cloud cover, daytime high temperature around -20 C, light southerly wind, no snow expected.
On Wednesday and Thursday wind slab development was noted in the Kakwa, more details and images here.
On Wednesday there were reports of numerous natural avalanches 20 to 40 cm in depth running at and above treeline. A southwest slope produced a size 3 natural avalanche. These avalanches presumably ran on surface hoar which was producing very touchy conditions. There are some great visuals of this activity in this MIN.
Since Wednesday the north has gotten 16 to 20 cm while the south half of the region has received 25 to 40 cm, with the Renshaw being the big winner.
This means that there is now 40 to 80 cm of snow resting on buried surface hoar which is most prevalent above 1600 m, it likely reaches into the alpine too, we're just not sure how high it extends.
Below 1600 m this snow is resting on a crust.
There may also be a more deeply buried layer of surface hoar around Pine Pass. See this MIN post here.
There are presently no deeper concerns in the snowpack.
