Recently formed wind slabs remain sensitive to human triggering. Use extra caution in wind-affected terrain and avoid freshly wind-loaded pockets of snow.
Confidence
Moderate - Wind effect is extremely variable
Weather Forecast
Expect a mix of sun and cloud with isolated flurries on Monday and Tuesday. Generally clear skies are forecast for Wednesday. Ridgetop winds are expected to remain mainly strong from the southwest on Monday and Tuesday and then drop to light on Wednesday. Freezing levels should hover around valley bottom for the forecast period. For a more detailed weather overview, check out our Mountain Weather Forecast at avalanche.ca/weather.
Avalanche Summary
No new avalanches have been reported, but this may speak to a lack of observations rather than actual conditions. On Sunday natural and human-triggered wind slab avalanches to size 1.5 were reported in the neighbouring Lizard / Flathead and Waterton Regions. I would expect similar conditions in the South Rockies. Continued wind slab activity is expected at higher elevations with new snow and strong southwest winds forecast for Sunday night.
Snowpack Summary
15-30cm of old storm snow is bonding poorly to the old snow surface buried early January. However, east of the divide there has been much less recent snow and much more wind. Extensive scouring has been reported in some areas and and stiff wind slabs exist in lee features at treeline and in the alpine. In areas that have seen less wind, recently formed wind slabs are likely softer, deeper, and may overlie surface hoar, facets, and/or a sun crust which formed at the start of January. The early December crust can be found down around 60-90cm. It is not currently expected to pose an avalanche problem but could wake-up in the future with substantial warming or heavy snow loading.
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.