Regions
Kootenay Boundary.
High temperatures and solar warming are driving the hazard ratings at this time. Conservative route selection and cornice avoidance are the theme for the next few days.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
A weak front will move onto the coast Friday night bringing light precipitation to the coast ranges and spotty precipitation to the Interior on Saturday. A stronger front will move onto the coast late Saturday through Sunday bringing light precipitation to the interior. On Sunday another pulse of moisture will pass through the region bringing 5 to 10cm of snow at higher elevations. Freezing levels will rise to near 2500 metres across the south on Friday but should begin to fall on Saturday.
Avalanche Summary
Reports of avalanche activity have slowed down in the region, but sluffing has been reported in steep north facing terrain and a size 2.5 avalanche, N. aspect, appears to have ben triggered recently by sledders. Loose wet avalanches are being reported, starting in steep terrain on solar aspects.
Snowpack Summary
There is now a complex snow pack in the region. Wind slabs still exist in lee terrain and may be problematic at high elevation on north and east aspects. The storm slab is now sitting on a melt-freeze crust that formed during the 2nd week of February and has been reported at various levels from 50 to 100cm throughout the region. This crust is widespread and may co-exist with surface hoar or weak facets. This interface is a critical layer to watch in the region, although it now appears to be bonding with the layers above and below it. A large trigger, such as cornice failure, or perhaps a wind slab avalanche could make this layer react and create a large, destructive avalanche. Warm temperatures may also make this layer reactive. Buried surface hoar from January is still being reported throughout the region and noted as a serious layer below 1800m. Surface hoar growing up to 8mm has been reported in the past few days. Sun crust may exist on solar aspects at the surface and has also been reported in the region 20cm below the surface. Daytime heating will help settle the snowpack but could also make for touchy conditions on south facing slopes in the afternoon.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
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.