Avalanche Forecast
Issued: Mar 4th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
mconlan,
Avalanche Canada
A high freezing level and sunny skies may re-awaken the buried surface hoar layer. Watch out on sun-exposed slopes during the heat of the day, and note that cornices will weaken and wind slabs may linger. Conservative terrain travel is recommended to avoid these problems.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
WEDNESDAY NIGHT: Partly cloudy, light southwest wind, alpine temperature -8 C.
THURSDAY: Clear skies, moderate southwest wind, alpine temperature -1 C, freezing level 1700 m.
FRIDAY: Cloudy with snowfall, accumulation 5 cm, moderate southwest wind, alpine temperature -4 C, freezing level 1500 m.
SATURDAY: Cloudy with snowfall, accumulation 10 to 15 cm, moderate southwest wind, alpine temperature -5 C, freezing level 1000 m.
Avalanche Summary
A handful more avalanches were triggered by riders on the February 22 surface hoar layer described in the Snowpack Summary. The avalanches were on north to east aspects, they were 20 to 50 cm deep, and they occurred around 2000 to 2300 m. The avalanches were small (size 1 to 1.5) to large (size 2).Â
Similar avalanches have been observed in the region for the past week, being generally small to large (size 1 to 2) and between 1800 and 2300 m on northwest to east aspects. This trend is suspected to continue as this layer slowly gains strength. Activity may increase on Thursday with a warming trend and sunny skies.
Snowpack Summary
Wind slabs may be found in lee terrain features at higher elevations due to wind transport from southwest wind. They may be around 10 to 20 cm thick immediately adjacent to ridges.
Around 30 to 50 cm of snow overlies a touchy layer of feathery surface hoar crystals. 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.
An older layer of surface hoar buried on February 13th now sits around 60 to 80 cm deep. This weak layer has been problematic in the east of the region between Nelson and Kootenay Pass. While it is likely gaining strength, there is uncertainty around lingering reactivity of this layer. Shallower avalanches may have the potential to step-down to this layer.Â
The remainder of the snowpack is strong and well-settled.
Terrain and Travel
- Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Persistent Slabs
Around 30 to 50 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. The likelihood of triggering this layer on Thursday may increase due to a spike in the freezing level along with sunny skies. 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
Wind Slabs
Wind slabs may continue to be reactive to skier traffic. Strong southwest to westerly wind has formed wind slabs in lee terrain features at higher elevations, particularly near ridges. Wind slabs could step down to buried weak layers and form larger avalanches.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 5th, 2020 5:00PM
