Human triggered avalanches at treeline remain possible, but time and cold temperatures have reduced their sensitivity to triggering. Watch for wind slabs in funny places in the alpine as easterly winds continue to blow.
Wind slabs formed last week have likely grown old and tired, but we're expecting more wind from the northeast, east and southeast this week which could form fresh wind slabs in unusual locations.
A surface hoar layer buried near the end of January is now down 40 to 80 cm and was quite sensitive to human triggering last week. Cold temperatures have likely helped to reduce activity on this interface, but it's still there and human triggered avalanches remain possible. This layer has been the most sensitive right at treeline, but it may extend into the lower alpine too.
Brrrr! Cold temperatures look to be with us through the weekend. The weather models are hinting at more seasonal temperatures beginning Tuesday.
WEDNESDAY NIGHT: Overnight low temperature around -38 C, moderate northeast wind, no snow expected.
THURSDAY: A few clouds, daytime high temperature around -20 C, moderate to strong east/southeast wind, no snow expected.
FRIDAY: A few clouds, daytime high temperature around -18 C, moderate to strong east/southeast wind, no snow expected.
SATURDAY: Clear skies at dawn with cloud cover steadily increasing through the day, daytime high temperature around -16 C, strong southeast wind, no snow expected.
There were a few small human triggered avalanches reported around treeline near Pine Pass last weekend. These failed on the recently buried surface hoar layer.
There were some other observations from throughout the region over the weekend that would suggest ongoing instability associated with that weak surface hoar layer. Reports ranged from whumpfs and shooting cracks, to visual observations of large surface hoar crystals
On February 3rd 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.
There is about 40-80 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 sits on a crust.
There are presently no deeper concerns in the snowpack.
