Avalanche Forecast
Issued: Jan 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
kdevine,
Avalanche Canada
Recent heavy snowfall means that storm slabs will be widespread and easy to trigger. Don't let the nicer weather lure you into bigger terrain.
Be aware of the potential for solar triggered avalanches. With so much new snow, it may not take much sun to trigger avalanches.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
WEDNESDAY NIGHT - Cloudy with clear periods / moderate northwest wind / alpine low temperature near -12
THURSDAY - Mainly sunny / moderate northwest wind / alpine high temperature near -5Â
FRIDAY - A mix of sun and cloud / moderate to strong west wind / alpine high temperature near -2 / alpine temperature inversion / freezing level 1500 m
SATURDAY - A mix of sun and cloud / moderate southwest wind / alpine high temperature near -6
Avalanche Summary
With a lot of new snow and recent strong to extreme winds, storm slab avalanches will probably be easy to trigger on Thursday, especially in wind loaded areas, and on sun-exposed slopes.
It is very likely that a natural avalanche cycle occurred on Tuesday night and into Wednesday during the storm.
A large (size three) cornice triggered persistent slab avalanche was reported on a large south-facing alpine slope in the Crowsnest Pass area last Thursday. This avalanche failed on weak facets overlying a hard crust deep in the snowpack and is an example of the "low probability; high consequence" scenario that persistent slab problems often create. View the MIN report HERE.
Snowpack Summary
The region received 15-30 cm of new snow between Tuesday night and Wednesday, with strong to extreme westerly winds. Storm and wind slabs are likely widespread and reactive.
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
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Avoid freshly wind loaded terrain features.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Up to 30 cm of recent fresh snow fell in the region with significant winds. Triggering storm slabs will be most likely in wind loaded areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Triggering large avalanches on weaknesses in the lower snowpack remains a possibility, especially since the new snow has added load to these weak layers. 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 14th, 2021 4:00PM
