Regions
Kootenay Boundary.
There is wide variability in the weather forecast for air temperature and cloud cover on Saturday. The forecast herein is assuming warm, above-freezing air temperature at high elevations.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
FRIDAY NIGHT: Increasing clouds, freezing level 800 m.SATURDAY: Cloudy, light northwest winds, alpine temperature variable between -1 C and 5 C, freezing level rising to 2000 m with inversion conditions possible.SUNDAY: Cloudy with trace snowfall, moderate to strong northwest winds, alpine temperature near 0 C, freezing level dropping from 2000 m to below valley bottom.MONDAY: Mostly clear skies, light northwest winds, alpine temperature -9 C, freezing level below valley bottom.
Avalanche Summary
On Thursday, a couple 15 cm thick slab avalanches were triggered by skiers on south to east aspects. The avalanches likely released on the surface hoar layer described in the Snowpack Summary.Looking towards the weekend, the likelihood of triggering the layers discussed in the Snowpack Summary may increase. Also expect loose wet avalanches if the air temperatures reach as warm as the weather forecast predicts.
Snowpack Summary
Warm air temperatures may moisten the snow surface on all aspects, with the most pronounced warming expected on southerly aspects. Below this, a rain crust exists about 10 to 20 cm beneath the surface. At depths of around 20 to 50 cm, expect to find a sun crust on south aspects and feathery surface hoar crystals in sheltered and shaded areas. The surface hoar may be most pronounced at treeline elevations.The remainder of the snowpack is generally reported as well-settled.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.