Storm expected to start around midday Saturday. Avalanche danger increasing.
Summary
Confidence
Fair - Due to the number of field observations
Weather Forecast
A storm is expected to start on Saturday around noon and persist overnight Saturday and into Sunday. Snow amounts are expected to be 5-10 cm on Saturday afternoon, 15-25 cm from 4pm Saturday to 4am Sunday and a further 5-10 cm for the rest of Sunday. Freezing levels are expected to be around 1300 m on Saturday and then peak around noon on Sunday at around 1700 m. Ridgetop winds are expected to be around 50 km/h from the south on Saturday and 70 km/h from the southwest early on Sunday morning. Monday should stay mostly dry, with freezing levels around 1500 m and winds dropping to around 30 km/h.
Avalanche Summary
On Wednesday, explosive testing produced small (size 1.5) avalanches on S to SE aspects at 2200 m in steep rocky terrain that were suspected to step down to the early November crust.
Snowpack Summary
10-20 cm new snow has buried a prominent surface hoar layer above a thick rain crust that extends as high as 2100 m. The crust/surface hoar interface is expected to produce a very good sliding layer once more snow falls, and avalanches that run on this layer could travel far as a result. High elevation north aspect slopes do not have the rain crust, but on these slopes, facets or buried surface hoar from earlier in the month may be lurking under dense storm slabs. Recent snowpack tests at 2050 m in a NW aspect in Kootenay Pass produced moderate sudden results down 35 cm under the late-November crust and down 79 cm on facets above the early-November crust. There is a possibility that additional load from lots of new snow, or a large trigger such as a cornice release could still trigger a deeper slab on shady aspects at high elevations.
jfloyer,
Avalanche Canada
