Triggering persistent slab avalanches may still be possible at lower elevations.
Summary
Confidence
High - Due to the number and quality of field observations
Weather Forecast
SATURDAY NIGHT: Light flurries of low density snow with accumulations up to 5 cm, light northeast wind, alpine temperatures drop to -15 C.SUNDAY: Light flurries with some clearing later in the day, light northeast wind, alpine temperatures around -14 C.MONDAY: Mix of sun and cloud, moderate northwest wind, alpine high temperatures around -14 C.TUESDAY: Cloudy with some isolated flurries, light northwest wind, alpine high temperatures around -12 C.
Avalanche Summary
Several small (size 1) wind slab and storm slab avalanches were triggered by skiers on Friday. These were predominantly on north and east aspects at all elevations. Also, a few small (size 1-1.5) persistent slab avalanches were triggered on northeast aspects (failing on the mid-January surface hoar layer). In the south part of the region, numerous size 1-2 wind slab, storm slab and persistent slab avalanches were reported every day between Tuesday and Friday. These were predominantly at treeline and in the alpine on all aspects.
Snowpack Summary
Relatively light amounts of low density snow have been accumulating above old surfaces that include previously wind-affected slopes, sugary facets and/or feathery surface hoar. In the south of the region, amounts since Tuesday are approximately 40 cm, while in the north, amount are more like 15 cm. Strong northeast winds have blown this snow into wind slabs onto unusual south- to west-facing slopes. The wind slab is reported to be very touchy, since it lies directly over this upper weak layer.Lower down in the snowpack there are two additional weak layers of surface hoar, which have produced large avalanches in the region. A layer buried at the end of January is around 40 cm deep and a layer buried mid-January is between 50 and 90 cm deep. The mid-January layer may also be associated with a melt-freeze crust on southerly aspects. These layers are most prominent at treeline and below.The remainder of the snowpack is generally well-settled. However, there have been sporadic reports of very large avalanches that have released near the base of the snowpack. Most of the avalanches have been in the high alpine. There has been about one report a week for the past month.
shorton,
Avalanche Canada
