South Rockies

Strong winds and new snow are likely to promote avalanche activity on Friday, especially in steep, wind affected terrain.

Moderate - Intensity of incoming weather systems is uncertain

Friday: Around 10 cm new snow expected, ridgetop winds 60-90 km/h from the southwest, treeline temperatures rising to around -5C. Low elevation winds are expected to also be strong. Saturday: mostly dry with some good sunshine. Winds westerly. Treeline temperature dropping to around -16C. Sunday: light snowfall starting late in the day, strong southwest winds, temperatures around -8C.

On Monday, a couple of size 2 avalanches were reportedly triggered by skiers in steep north and northeast facing slopes. Since then no further avalanches have been noted in this region. I anticipate the chance of both natural and human triggered avalanches will increase during the expected storm on Friday.

The series of recent storms has left us with around 40-60 cm new snow sitting on a firm rain crust. For the most part, the new snow has bonded well to this rain crust, although potentially unstable wind slabs could exist where wind-pressed snow rests directly on a slippery crust below. A previous weak layer from early December consists of crust, surface hoar, and/or facets and is typically down 70-90cm. Around 20-30cm below this interface is a rain crust from mid-Nov with a thick layer of facets below it. Both the early-Dec and mid-Nov layers have become dormant and are likely being capped at treeline and below by the more recent rain crust layer. However, these layers may still be reactive to heavy triggers such as cornices, explosives, or smaller avalanches stepping down.