Avalanche Forecast
Issued: Mar 7th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
mconlan,
Avalanche Canada
This weekend's snow is forming new slabs and loading a buried weak layer. Don't be complacent, as the buried weak layer continues to surprise people. Use caution on sun-exposed slopes when the sky clears.
Summary
Confidence
High - The snowpack structure is generally well understood.
Weather Forecast
SATURDAY NIGHT: Mostly cloudy with isolated snowfall, accumulation 2 to 5 cm, light southwest wind, alpine temperature -7 C.
SUNDAY: Mix of sun and cloud with isolated flurries, 2 to 5 cm in the east of the region, moderate southwest wind, alpine temperature -9 C, freezing level 1000 m.
MONDAY: Clear skies, light southwest wind, alpine temperature -7 C, freezing level 1200 m.
TUESDAY: Mix of sun and cloud, light southwest wind, alpine temperature -6 C, freezing level 1200 m.
Avalanche Summary
On Friday, a few more small (size 1.5) avalanches released on the surface hoar layer described in the Snowpack Summary. They occurred on northerly aspects around 2000 m and were 20 to 30 cm deep.
Over the past two weeks, small to large (size 1 to 2) avalanches have released on the surface hoar layer. They have most often released between 1800 and 2300 m on northwest to east aspects. This trend is suspected to continue as this layer slowly gains strength.
Snowpack Summary
Around 10 cm of snow fell in the west of the region and 15 to 30 cm in the east of the region on Saturday. Storm slabs are likely developing as the snow consolidates. The wind remained light to moderate from the southwest, so wind slab formation may be limited to immediate lee features.
The snowfall is loading a touchy layer of feathery surface hoar crystals that is found 30 to 60 cm deep. The layer is most commonly found in open trees (e.g. in this MIN) or sheltered terrain around upper below treeline, treeline, and lower alpine elevations. Check out the latest forecaster blog that offers a deeper dive into these conditions.
The remainder of the snowpack is strong and well-settled.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Carefully evaluate steep lines for wind slabs.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
Problems
Persistent Slabs
Around 30 to 60 cm of snow overlies a weak layer of surface hoar. The layer has been most problematic on northwest to northeast aspects between 1600 m and 2300 m, but the layer may exist on all aspects and at all elevations. Riders will be capable of triggering this layer for some time until there is a substantial change in the snowpack. Assess the layer prior to committing to avalanche terrain or adopt a conservative mindset to avoid the problem.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
Around 15 to 30 cm of snow fell in the region, with the most in the east (e.g., Kootenay Pass). As this snow consolidates, it will form storm slabs. The snow may have formed slab properties in lee terrain features, as the snow fell with light to moderate southwest wind. If triggered, storm slabs could step down to the buried surface hoar layer, forming large avalanches. Use added caution on sun-exposed slopes when the sun is shining, as it could rapidly deteriorate the storm snow and cause loose or slab avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 8th, 2020 5:00PM
