Regions
Kootenay Boundary.
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Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
There is no precipitation in the forecast. The freezing level should drop down to the valley bottoms overnight and then rise up to about 1500 metres during the day on Monday. This pattern is expected to continue for Tuesday and Wednesday. The only uncertainty is how much sun we will see over the next few days. There is a chance of valley cloud and high cloud each day.
Avalanche Summary
On Saturday there was one loose wet avalanche size 2.0 that released from a steep northeast aspect at treeline. I suspect that cooler alpine temperatures and the re-freezing has reduced the likelihood of triggering deeply buried weak layers. Some loose wet avalanche activity may continue if we see strong solar radiation.
Snowpack Summary
Alpine temperatures dropped down to about -7 overnight and the freezing level dropped down close to valley bottoms. This cooling down of the snowpack is expected to develop new melt-freeze crusts on the surface and reduce fracture propagations at buried weak layers. During the warm-up we found approximately 65-100 cm of recent storm snow that is bonding well to a crust buried at the beginning of February; however, this bond is much weaker where surface hoar overlies the crust. Below that, recent snowpack tests gave moderate to hard but sudden collapse results on the mid-January surface hoar where it was found down 70-80 cm on a northeast facing treeline slope. This persistent weakness has been found as deep as 110 cm, or deeper on wind-loaded slopes. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.