Recently formed wind slabs have been slow to settle and gain strength. Use extra caution around ridge crests.
Weather Forecast
On Wednesday evening, the first of 2 organized fronts will move through the region bringing 5-10cm of new snow and strong southwest winds. Thursday will see mainly overcast skies and continued strong ridgetop winds. By Friday evening, the second front will pass through the region. Expect another 5-10cm of snow and strong southwest winds. Freezing levels should remain at valley bottom for Wednesday and Thursday, and then rise to about 1500m for Friday.
Avalanche Summary
On Monday, a skier triggered a size 2 wind slab avalanche on a southwest aspect at about 2250m in the Revelstoke backcountry. The individual was taken for a ride, but was uninjured. Although existing wind slabs should gain strength over time, new snow and wind on Wednesday night should spark a new round of wind slab activity on Thursday . There is also the ongoing possibility of triggering more destructive persistent slab avalanches in isolated terrain.
Snowpack Summary
Snowfall and strong winds prior to last weekend created wind slabs that remain sensitive to light inputs in higher elevation lee terrain. The recently destructive surface hoar layer from early January is now typically down 80-120cm in most places. Although the layer has become harder to human trigger and is variably reactive in snowpack tests, it still has the potential for wide propagations. With that, I would continue to show respect for this layer in steep, open terrain at treeline and below. In general, the lower snowpack below this layer is well settled and strong.
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.