Avalanche Forecast
Issued: Jan 19th, 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.
ahanna,
Avalanche Canada
Be careful around open slopes and convex rolls at treeline and alpine elevations. These slopes may have fresh wind slabs and/or buried surface hoar layers.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Partly cloudy, strong to extreme ridgetop wind easing to moderate west, freezing level valley bottom.
WEDNESDAY: Mix of sun and cloud, moderate northwest ridgetop wind, treeline temperatures around -7 C.
THURSDAY: Mix of sun and cloud, light wind, treeline temperatures around -8 C.
FRIDAY: Sunny, light wind, treeline temperatures around -11 C.
Avalanche Summary
On Sunday skiers triggered a few small slab and loose avalanches (size 1).
Since last week's storm a few natural avalanches are suspected to have run on the surface hoar 20-50 cm down, including a size 2.5 storm slab out of a northwest facing gully feature around 2000 m near Nelson.
Snowpack Summary
Strong overnight wind has likely redistributed 10-15 cm of recent snow into wind slabs in lee terrain features at upper elevations. This snow may sit over a widespread crust that extends up to around 2000 m, or large surface hoar crystals in wind sheltered areas above the crust elevation. In areas such as Rossland where the thick crust caps the snowpack to mountaintop, avalanches are unlikely but travel is difficult.
A layer of surface hoar may be found 20-50 cm below the surface, particularly in areas around Nelson. Some recent avalanches have run on this layer and where it has been found in snow profiles, it has been producing moderate to hard planar test results.
A couple of crusts with weak faceted grains overtop are buried deep within the snowpack. The upper layer is 80 to 130 cm deep and the lower is near the ground. A few large avalanches ran naturally on these layers last week near Rossland. More recently, some large cornice falls have have been good slope testers. Some triggered storm slabs but none stepped down to these deeper layers. While this is a good indicator for stability, the potential may linger for triggering a deep slab in steep, rocky, thin snowpack areas.
Terrain and Travel
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be carefull around freshly wind loaded features.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Problems
Wind Slabs
Strong overnight wind has likely redistributed small amounts of recent snow into wind slabs in lee terrain features at upper elevations. They could be especially reactive where they sit over a rain crust or large surface hoar crystals.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Reports suggest some slopes at treeline have a weak layer of surface hoar 30-50 cm below the surface. An avalanche cycle cleaned out this layer in many areas, but in places where avalanches have not yet run, it remains a concern. Use caution around convexities in open trees.
Aspects: All aspects.
Elevations: Treeline.
Likelihood
Expected Size
Valid until: Jan 20th, 2021 4:00PM
