Avalanche Forecast
Regions: South Columbia.
Keep an eye on the wind. Avalanche hazard will likely increase throughout the day as the strong winds build small but reactive slabs.
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Friday night: light northwest winds with no new snow expected. Low of -27 at 1500m,
Saturday: Moderate to strong west winds with up to 5cm of new snow. High of -15 at 1500m.
Sunday: strong southwest winds in the alpine with light snow all day accumulating up too 10cm with the largest snowfall amounts in the Monashees. High of -14 at 1500m.
Monday: light snow all day with light to moderate southwest winds in the alpine. High of -7 at 1500m.
Avalanche Summary
Recently a size 2.5 natural avalanche was reported in the Selkirks. This avalanche was on a northwest aspect at 2100m and failed on the early December facet crust combo. The crown was up to 150cm deep, a good indicator of the deadly consequences of being involved in an avalanche failing on this deep layer.
Numerous small to large (size 1 to 2) slab avalanches were triggered naturally and by riders on Wednesday. They occurred on all aspects, were often 10 to 40 cm deep, and generally at treeline and alpine elevations. A few of the avalanches were wind slabs, and it is possible that some of the others released on the surface hoar layer described in the snowpack summary.
Snowpack Summary
New wind slab will form throughout the day on Saturday on north and east aspects. These new slabs will form over faceted and wind effected surfaces, this will likely result in a poor bond.
A weak layer of feathery surface hoar may be found around 30 to 50 cm deep. It is most likely found in sheltered terrain features in the lower alpine and treeline, or open features below treeline (e.g., cut blocks). To date, this layer has been most active in the southern half of the region.
Sugary faceted grains may be found around the early-December melt-freeze crust 70 to 150 cm deep. The layer is most prevalent around 1700 m to 2400 m but could exist at lower and higher elevations for sections of the region. This layer is spatially variable, with many areas showing good bonding to the crust whereas other areas showing concern. This layer has recently been most reactive where it remains shallower than about 100 cm.
Terrain and Travel
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
Avalanche Problems
Wind Slabs
New wind slabs will form throughout the day on Saturday. These new slabs will likely be limited in size but sensitive to rider traffic due to the fact that they will form over faceted and wind effected surfaces. Strong winds mean that these slabs could be found further down slope then expected. Sensitivity to triggering will be greatest where wind slab has formed over Surface hoar in the treeline and below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
We continue to receive sporadic reports of large avalanches on a weak layer of faceted grains around a melt-freeze crust that formed in early December. This layer is found around 70 to 150 cm deep and is most common at elevations between 1700 m and 2400 m. Read more about it here.
There is also a layer of weak surface hoar found about 25 to 50 cm deep, generally in terrain features sheltered from the wind. This layer may be more prevalent in the southern half of the region. Investigate for this layer prior to committing yourself to consequential terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5