Regions
Northwest Inland.
In the west of the region where recent accumulations were the greatest, new wind slabs are expected to be deeper and more reactive.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Warm, wet and windy conditions will persist for Wednesday and Wednesday night. Expect between 5-8mm of precipitation, extreme southerly winds and freezing levels at about 1700m. On Thursday, the region should see generally light flurries, strong southwest winds and freezing levels dropping to about 1200m. By Friday, a pattern shift should bring generally overcast skies, decreased winds and freezing levels closer to 600m.
Avalanche Summary
There are very few recent observations from the region. A couple natural size 2 slab avalanches were observed in wind-loaded terrain (N-NE aspects) at around 1800 m last Friday. Light to locally moderate amounts of new snow and extreme southwest winds likely sparked a new round of wind slab activity on Tuesday.
Snowpack Summary
On Monday night a few centimetres of new snow fell in the mountains around Smithers while closer to 15 cm fell in areas further west. Strong to extreme winds have likely redistributed much of this new snow into reactive wind slabs at higher elevations while lower elevation surfaces are likely now moist due to rising freezing levels during the system. There is a notable persistent weakness of buried surface hoar in many places, generally found between 30 and 60 cm deep. Wind, sunshine, and milder temperatures could help promote slab development in the snow overlying this interface. Stay tuned to signs of instability like recent avalanches, whumpfing, and shooting cracks. The mid pack that was reported to be well settled may have now facetted in the shallower areas, and the deeper basal layers are almost certainly facetted and weak.
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.