Wind slabs up high and the potential to trigger a couple buried weak layers are keeping our guard up.
Wind slabs may be found in exposed terrain features near ridges. They could remain touchy to riders, as they may sit on weak faceted snow or surface hoar crystals.
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.
THURSDAY NIGHT: Partly cloudy with no precipitation, 10 to 20 km/h northwest wind, alpine temperature -21 C.
FRIDAY: Clear skies with no precipitation, 10 to 20 km/h northwest wind, alpine temperature -20 C.
SATURDAY: Increasing clouds with afternoon snowfall, accumulation 1 to 3 cm, 20 to 40 km/h southwest wind, alpine temperature -17 C.
SUNDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 30 to 60 km/h southwest wind, alpine temperature -14 C.
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.
The latest persistent slab avalanche occurred on Tuesday, occurring in alpine terrain on a northeast aspect. It was very large (size 3 to 4) and indicates that this layer remains capable of forming large and destructive avalanches.
Thin wind slabs may have formed from Wednesday night's 5 cm of snow and variable wind. These slabs could remain touchy to riders, as they sit on previously wind-affected snow, sugary faceted grains, and/or surface hoar in areas sheltered from the wind.
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.
