Regions
Northwest Coastal.
Uncertainty with regards to the new storms forecast to hit the coast over the next few days. Stay tuned for more information regarding the developing avalanche danger this weekend.
Weather Forecast
Overcast with flurries or light snow combined with increasing southwest wind overnight. Freezing level around 500 metres on Wednesday with moderate southwest winds and 5-10 cm of new snow (more snow nearer to the coast). Another 5-8 cm of new snow by Thursday morning and 5-10 cm more during the day combined with strong southerly winds and freezing levels rising up to 1300 metres. Snow continuing on Friday with strong to extreme south winds and freezing levels around 1500 metres. The weekend also looks wet and windy, and some models suggest that heavier precipitation may arrive by Friday.
Avalanche Summary
No new avalanches reported from skiable terrain in the south. Some natural windslabs continue to release in the Bear Pass alpine up to size 1.5 in steep terrain. Triggering wind slabs as well as lingering persistent slabs remains a possibility at higher elevations.
Snowpack Summary
Light flurries and moderate winds have formed fresh wind slabs above 40-60 cm of settled storm snow from last week. Freezing levels reached 1200 m during the storm, which has left a hard supportive crust at lower elevations. At this point there is some uncertainty as to how deeper persistent weak layers are responding to the recent loading and warming. Several weak surface hoar and facet interfaces were reactive during the storm, but have shown signs gaining strength since. This includes the January 5th layer about 50 cm deep and the December 25th layer up to a metre deep. These are not typical conditions for this coastal region, and it will take more time to gain confidence about the distribution and likelihood of triggering these deeply buried weak layers.
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.