Kootenay Boundary

The cooling trend continues to reduce the avalanche danger.

Fair - Timing or intensity of solar radiation is uncertain

The freezing level is expected to drop down to valley bottoms overnight and then rise up to about 900 metres on Friday. Friday should be mostly sunny with valley cloud and light winds. There is a chance of a weak above freezing level in the alpine between 2000 – 2500 metres during the day. Saturday should be a mix of sun and cloud with valley cloud persisting and winds becoming moderate from the Northwest. Precipitation is expected to start early Sunday morning and continue during the day with 5-10 mm forecast.

There are no new reports of avalanches. On Monday there were several size 2.0-2.5 loose wet and wet slab avalanches released with explosives at Kootenay Pass, and a size 3.0 natural avalanche in the backcountry near Whitewater ski resort on a Southeast aspect with a very wide propagation that probably released on the mid-January persistent weak layer during a period of strong solar radiation. Moist or wet loose snow avalanches have been reported from several areas up to size 2.0 over the past few days during the warming event. On Saturday a skier triggered a size 2 persistent slab which failed on the mid-December layer. This was a surprising result because it was on a well-supported, concave terrain feature (which had also been heavily skied).

The cool down has started. Overnight freezing down to valley bottoms has created melt-freeze crusts. Strong solar radiation and warm temperatures are affecting the surface layers and turning them moist or wet. We are in a spring like diurnal freeze/thaw cycle. Periods of warming has increased the likelihood of triggering the persistent weak layer of mid-Jan surface hoar layer which is down about 20-60 cm. These large, well-preserved surface hoar crystals sit on a thin crust up to about 1900m on north aspects and all the way to ridgeline on south aspects. A deeper crust/surface hoar combo buried in mid-December is typically down 80-120cm and has produced some large avalanches recently.