Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Regions
South Rockies.
Professionals are tip-toeing in the South Rockies due to the possibility of triggering a deeply buried weak layer. Avoid thin, rocky or sparsely treed slopes.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SATURDAY: Mix of sun and cloud, with a few flurries possible. Freezing level at valley floor. Light to moderate westerly winds.SUNDAY: Cloudy with flurries. Freezing level near 800 m. Moderate south-westerly winds.MONDAY: Mainly sunny. Freezing level near 600 m. Moderate westerly winds. More details can be found in the Mountain Weather Forecast.
Avalanche Summary
There have been no avalanches reported over the last couple of days, however observations of some very large slabs were made in the North Elk valley. These are thought to have failed within the last week. Whumpfing was reported at treeline in the North Elk valley as well.It is still possible to trigger a surprisingly large wind slab or persistent slab with the weight of a person or sled, especially from a convexity or thin snowpack area. If the sun is shining, avoid exposure to steep solar aspects where loose wet avalanche activity is possible.
Snowpack Summary
You are likely to find variable surfaces in open terrain after recent strong winds took out their fury on the upper snowpack. Fragile cornices and hard and soft wind slabs can be found on many alpine and treeline slopes. Ongoing strong winds are expected to keep building wind slabs, which overlie a spotty crust/surface hoar interface. The lower snowpack is weak with two primary concerns:1) A widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2) A rain crust with sugary facets buried in late-November near the bottom of the snowpack.Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.