Regions
Kootenay Boundary.
Reports of whumpfing indicate a weak layer buried at the beginning of January may still be sensitive to light loads. Choose conservative terrain and watch for clues of instability.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Expect a mix of sun and cloud with isolated flurries on Tuesday and Wednesday. Ridgetop winds should be light to moderate from the southwest on Tuesday switching to light and northwesterly on Wednesday. A Pacific system will move into the region on Thursday bringing steady snowfall and strong southwest winds. Freezing levels should sit at or near valley bottom for the forecast period.
Avalanche Summary
Over the weekend we had limited observations of new avalanches. With the forecast static weather pattern I expect a drop in natural avalanche activity; however, human triggered persistent slab avalanches remain a concern in many areas.
Snowpack Summary
10-15 cm of new snow and moderate southerly winds have likely created fresh wind slabs in high elevation lee terrain. 35-60 cm below the surface you'll find a weak layer of well-developed surface hoar and a hard crust on steep solar aspects. Ongoing Mountain Information Network reports of whumpfing and shooting cracks show this layer is still sensitive to light loads. I would anticipate increased reactivity at this interface in areas where the overlying slab is deep and has gained cohesion through wind pressing, warming, and/or settlement. The mid and lower snowpack are generally well settled and strong.
Problems
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.
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.