Avalanche Forecast
Issued: Jan 18th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
jleblanc,
Avalanche Canada
Variable conditions exist throughout the region, with increased recent snow amounts in the north. Keep your guard up as isolated pockets of wind slabs are still showing signs of reactivity.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Partly cloudy, light northwest wind, treeline temperatures around -6 C, freezing level lowering to valley bottom.
WEDNESDAY: Sunny periods, light north wind, treeline temperatures around -10 C, freezing level at valley bottom.
THURSDAY: Snow up to 5 cm, moderate-strong southwest wind, treeline temperatures around -6 C, freezing level rising to 1000 m.
FRIDAY: Sunny periods, light southwest wind, treeline temperatures around -6 C, freezing level rising to 1000 m.
Avalanche Summary
Reactive wind slabs have caught riders by surprise recently, with large (size 2) avalanches releasing on alpine lee features and open areas at treeline.
Over the last week, the early December persistent weak layer has produced few large natural avalanches (2-2.5) in the center of the region. Explosive controls have also produced few size 2 avalanches that failed on the same persistent weak layer, one being remotely triggered. These occurred on thin to thick features on northeast-facing slopes from between 1600 m and 2000 m, where the layer was buried 100 cm + deep. Although avalanche activity has tapper off, it remains a concern across the region.
Snowpack Summary
In the last two days, fresh snow has been redistributed on alpine lee slopes and open areas at treeline. Around 1900 m and below, a crust is now capping the dense 10-30 cm of snow which has settled significantly with the past mild temperatures. The crust varies from thin/breakable to thick/supportive, according to the aspects and elevation. Below the recent snow, a layer of feathery surface hoar and melt-freeze crusts are found, which seems to be still reactive in isolated pockets areas. Lower elevations have gone through a melt-freeze cycle with past elevated freezing level with elevated freezing levels.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-160 cm. Activity on this layer has been sporadic but has generally been triggered on steep, rocky slopes, with a shallow or thin-to-thick snowpack.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Wind Slabs
Pockets of reactive wind slabs are possible at upper elevations, where wind blows have blown recent dry snow into unstable slabs. While these slabs may be thin, they could be poorly bonded to the underlying snow, like a surface hoar/crust combo, so be extra cautious in lee terrain and convex rolls.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A deep persistent slab problem formed by a crust down 90-160 cm has created a low likelihood, high consequence scenario that is difficult to forecast. The old and deeply buried weak layer has produced a number of large and surprising avalanches over the past two weeks. This problem is likely to be triggered on steep, rocky slopes with a shallow or thin-to-thick snowpack. The same feature or path can slide repeatedly when the persistent weak layer is reloaded with recent snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 19th, 2022 4:00PM
