Avalanche Forecast
Issued: Dec 28th, 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
Wind slabs may be found in exposed terrain. Sporadic reports of avalanches on a buried weak layer are keeping our guard up.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
TUESDAY NIGHT: Mostly cloudy with isolated snowfall, 15 km/h northwest wind, alpine temperature -23 C.
WEDNESDAY: Clear skies with no precipitation, 20 to 40 km/h northwest wind, alpine temperature -23 C.
THURSDAY: Cloudy with snowfall, accumulation 5 cm, 20 to 40 km/h southwest wind, alpine temperature -23 C.
FRIDAY: Mix of sun and cloud with no precipitation, 15 km/h northeast wind, alpine temperature -22 C.
Avalanche Summary
A few wind and storm slab avalanches were triggered naturally and by riders on Tuesday. They were generally small to large (size 1 to 2), on all aspects, and at treeline and alpine elevations.
There have been a few reports of activity on the early-December weak layer described in the Snowpack Summary, including two natural avalanches and one triggered by a rider. They were generally large (size 2 to 3), on all aspects, and between about 1700 m and up to 2600 m.
Similar avalanche activity is possible for Wednesday, given similar weather conditions and cold temperatures limiting bonding of the snowpack.
Snowpack Summary
Cold air continues to facet the top of the snowpack. Elevated wind on Wednesday may produce new wind slabs on south to east aspects. Old wind slabs may still linger given the cold air, meaning wind slabs may be found on all aspects.
A weak layer of feathery surface hoar may be found around 30 to 50 cm deep in sheltered terrain, most likely around treeline or open features below treeline. Although avalanche activity hasn't been prominent on this layer, it has been reactive in snowpack tests.
Sugary faceted grains may be found around the early-December melt-freeze crust 80 to 150 cm deep. The layer is most prevalent around 1700 m to 2200 m but could exist at lower and higher elevations for pockets 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. 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.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Wind Slabs
New wind slabs are expected to form on south to east aspects over the course of Wednesday. Lingering wind slabs may still exist on northerly aspects, meaning you could trigger a slab on all aspects.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
We continue to receive sporadic reports of people triggering a weak layer of faceted grains around a melt-freeze crust that formed in early December. This layer is found around 80 to 150 cm deep and is most common at elevations between 1700 m and 2200 m.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 29th, 2021 4:00PM
