Avalanche Forecast
Issued: Dec 29th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
New wind slabs are expected to form on Wednesday night. Sporadic reports of avalanches on a couple buried weak layers are keeping our guard up.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 5 to 10 cm, 20 to 50 km/h southwest wind, alpine temperature -21 C.
THURSDAY: Mostly cloudy with isolated flurries, trace accumulation, 10 to 20 km/h northwest wind, alpine temperature -20 C.
FRIDAY: Clear skies no precipitation, 10 to 20 km/h north wind, alpine temperature -22 C.
SATURDAY: Increasing clouds with snowfall, accumulation 5 cm, 40 to 60 km/h southwest wind, alpine temperature -15 C.
Avalanche Summary
A few small (size 1 to 2) avalanches were triggered naturally and by riders on Tuesday. They occurred within the top 50 cm of the snowpack, with at least a couple of them occurring on the surface hoar layer described in the snowpack summary. They were mostly on west to northeast terrain features at treeline to alpine elevations.
Another persistent slab avalanche was observed, 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.
Snowpack Summary
A bit of new snow and strong wind are likely to form new wind slabs in exposed terrain Wednesday night. These slabs will overly previously wind-affected snow, sugary faceted grains, or surface hoar.Â
A weak layer of feathery surface hoar may be found around 30 to 50 cm deep. It is most likely to be found in sheltered alpine features, around treeline, or open features below treeline. Only a couple small avalanches have been reported on this layer but it is showing reactivity in snowpack tests.
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 been most reactive where it remains shallower than about 100 cm. Learn more about how to manage this problem here.
Terrain and Travel
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Carefully evaluate steep lines for wind slabs.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- 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.
Problems
Wind Slabs
Strong wind and a bit of new snow on Wednesday night may form new wind slabs in exposed terrain features at higher elevations. Slabs that form could be touchy, as they may overly weak faceted snow or surface hoar that formed during the clear, cold spell.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
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.
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
Expected Size
Valid until: Dec 30th, 2021 4:00PM
