Overnight snowfall and wind have likely formed widespread storm slabs which may become increasingly reactive with shifting wind and sun forecast for Sunday.
We recommend sticking to simple terrain while the new snow settles and buried weak layers adjust to the new load.
Weak surface hoar and/or faceted grains sit above a melt-freeze crust 50 to 100 cm deep. Be aware that new snow and wind will be adding additional load to this layer, and it may become reactive again this weekend.
Fresh storm slabs are likely to be especially reactive in wind loaded terrain features. Recent wind has varied in direction so these may be found on a variety of aspects. The fresh snow will also be sensitive to seeing the sun for the first time and rapid settlement may trigger natural releases.
Saturday night: Snow, 10-30 cm, heaviest snowfall near Kootenay Pass, strong southwest wind, freezing level 1400 m.
Sunday: Flurries up to 5 cm then clearing, moderate northwest wind, alpine high temperature near -5, freezing level 1300 m.
Monday: Snow, 5-15 cm, moderate south wind, alpine high temperature near -3, freezing level 1300 m.
Tuesday: Sunny, light southwest wind, alpine high temperature near -7, freezing level 1100 m.
Numerous size 1-2 explosive triggered storm slab avalanches were reported in the region on Thursday and Friday. Storm slab avalanche activity is expected to continue into Sunday. Predictable triggers include humans, wind and solar radiation.
With new snow slowly but steadily piling up, the chances of a resurgence of persistent slab avalanches will increase. This incremental loading will likely make it difficult to predict when this layer may once again reach a tipping point and start producing avalanches. This problem is best managed with conservative terrain selection.
10 to 30 cm of new snow is expected between Saturday night and Sunday afternoon, bringing storm totals to 30-60 cm. As winds shift from southwest to northwest on Sunday, wind loading patterns will continue to change at upper elevations.
Two weak layers are buried in close proximity to one another. They are 70-100 cm deep around Nelson and 50-80 cm deep around Rossland and other western parts of the region. The layers are composed of feathery surface hoar and sugary faceted grains and they overlie a hard melt-freeze crust.
