Avalanche Forecast
Issued: Jan 17th, 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.
dsaly,
Avalanche Canada
Dig down and investigate deeper layers in the snowpack before committing to big lines.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
SUNDAY NIGHT- Mostly cloudy / Moderate to strong west-northwest wind / Alpine high temperature near -5
MONDAY - Sun and cloud / Light northwest wind / Alpine high temperature near -6
TUESDAY - Cloudy with isolated flurries / Increasingly strong southwest wind / Alpine high temperature near -9
WEDNESDAY - Cloudy with sunny breaks / moderate to light west wind / alpine high temperature near -7
Avalanche Summary
On Thursday, explosives triggered a size 2.5 wind slab avalanche, and one natural size 3 persistent slab avalanche, both occurred on southeast aspects in the alpine.
Additionally on Thursday, a size 3 persistent slab avalanche was reported on an east aspect at 2400 m in the neighboring Waterton National Park region.
On Wednesday, were several natural avalanches to size 2.5 were observed and explosives also triggered avalanches up to size 2.5.
And just over a week ago (Jan 14), a natural size 3 persistent slab avalanche was reported on a large south-facing alpine slope in the Crowsnest Pass area.
These recent avalanches are a prime example of the "low probability; high consequence" scenario that persistent slab problems often create.Â
Snowpack Summary
Strong winds have polished and pressed snow into hard slabs and sastrugi and stripped windward slopes. A melt-freeze crust covers surfaces up to 1850 m.
The lower snowpack consists of decomposing crusts and weak, faceted snow. In the Elk Valley, a decomposing surface hoar layer can be found around one of these crusts 60-120 cm below the surface. Avalanche activity on these layers in the lower snowpack has been sporadic, mostly triggered by large loads such as a wind slab avalanche, or a cornice fall. These deeper weak layers are most likely to be human triggered on steep, rocky slopes with a shallow or thin to thick snowpack.
Terrain and Travel
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Be alert to conditions that change with elevation, aspect and exposure to wind.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Wind Slabs
Hard wind slabs may be stubborn, however slabs will be dense and firm when triggered.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Triggering large avalanches on weaknesses in the lower snowpack remains a possibility. In some areas the concern is weak snow around crusts 60 to 120 cm deep, while in others it's weak snow near the bottom of the snowpack. Human triggering of these layers are most likely in steep, rocky slopes with a shallow or thin to thick snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 18th, 2021 4:00PM
