New wind slabs have been reported to be deeper than expected and easy to trigger. New storm slabs are also reported to be easy to trigger and running fast on a combination of crusts and buried surface hoar.
Confidence
Fair - Due to variable snowpack conditions for the entire period
Weather Forecast
Overnight and Friday: There is a chance of a couple of cms overnight as a weak band of moist air moves across the region. Strong Northwesterly winds overnight are expected to diminish to moderate during the day. There may be a period of broken skies or mostly clear skies in the afternoon. Alpine temperatures are expected to be about -3.0 and the freezing level should be about 1300 metres.Saturday: The moist air on the South side of the trough is expected to bring 10-15 cms of snow to the region as it passes through from the Northwest. Upslope areas in the West Monashee may see enhanced snow fall amounts during periods of convective flurries as the trailing cold front passes.Sunday: The next weak ridge of high pressure is expected to develop over the interior, bringing cooler temperatures and drier conditions.
Avalanche Summary
Explosives control resulted in avalanches up to size 2.5 in the North Selkirks. Natural avalanches occurred in the highway corridor up to size 3.0, and in remote areas up to size 2.5. Skiers controlled avalanches up to size 1.5 and some were surprised by accidental releases up to size 1.0
Snowpack Summary
There is a lot of variability in the depth of the new snow slab and the new wind slabs. Areas that received 30-40 cms of new snow have developed thick new wind slabs at higher elevations that may be triggered by light additional loads. The storm slab in these areas has been reported to be reactive to skiers, as it slides easily on a layer of surface hoar that developed just previous to the latest storm. In some areas there is a sun crust that developed during the sunny weather last weekend that is a smooth and fast sliding layer for the new storm slab. Deeper weak layers continue to show planar results in snow profile tests down about 70 cms and also at about 100 cms. These deeper layers are less likely to be triggered by skiers, but cornice falls or other large triggers may step down and result in large avalanches.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.