Regions
Kootenay Boundary.
Cold north winds have been blowing. Be on the watch for wind slabs, particularly on southerly aspects
Confidence
Moderate - Due to the number of field observations
Weather Forecast
The arctic outbreak continues with cold temperatures and no snow until Sunday at the earliest. WEDNESDAY: Dry and sunny. Winds light north/northeasterly 5-15 km/h. Temperatures between -18 and -26 Celcius!THURSDAY: A mix of sun and cloud. Wind light west. Temperatures between -13 and -20 Celcius. No precipitation. FRIDAY: Cloudy with sunny periods. Wind becoming southwesterly 5-15 km/h. Temperatures between -12 and -20 Celcius. No precipitation.
Avalanche Summary
We've had reports of several natural and skier-triggered windslabs (Size 1.5-2) yesterday in the backcountry near Nelson. Aspects were southwest through north at treeline and in the alpine.
Snowpack Summary
This region saw 30-60 cm new snow during last week's storms (with more in the eastern areas and less in the west). The new snow sits over a weak layer buried on Boxing Day that was initially reactive but now appears to have gained strength. Recent winds switched from mainly southwesterly to northerly, "reverse loading" areas and causing windslabs. Slightly lower in the snowpack is an interface buried mid-December, now down 40-100 cm. This layer appears to be well bonded in many parts of the region but was reactive for a while last week west of Trail and Castlegar where preserved surface hoar was thought to be responsible for four small (but surprising) skier trigger avalanches. It will be important to continue to monitor this layer for further signs of reactivity.
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.