Avalanche Forecast
Issued: Feb 21st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
mconlan,
Avalanche Canada
Storm slabs are expected to form overnight and they may be particularly reactive to human traffic on Saturday. A conservative mindset will be important to manage this problem.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 to 15 cm, strong west wind, treeline temperature -2 C, freezing level 900 m.
SATURDAY: Mix of sun and cloud, moderate northwest wind, treeline temperature -2 C, freezing level 1000 m.
SUNDAY: Cloudy with snowfall, accumulation 15 to 20 cm, strong southwest wind, treeline temperature -2 C, freezing level 1000 m.
MONDAY: Mix of sun and cloud, light to moderate northwest wind, treeline temperature -5 C, freezing level 500 m.
Avalanche Summary
No new avalanches were observed on Thursday. Avalanche activity is expected to increase during and after Friday night's storm.Â
Snowpack Summary
Around 10 to 15 cm of snow is expected Friday night. The snow will fall onto a weak layer of surface hoar, which was reported to be 10 to 15 mm in size and on all aspects and elevations. The surface hoar overlies a breakable melt-freeze crust, meaning that the surface hoar will likely act as an easy sliding layer for the storm snow. The snow will also fall with strong westerly wind, so the deepest deposits will be in lee terrain features.
The remainder of the snowpack is well-settled.
The snowpack depth varies from around 200 to 250 cm at the peaks of the North Shore mountains (1400 m) and rapidly decreases with elevation to no snow below 1000 m.
Terrain and Travel
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Choose conservative terrain and watch for clues of instability.
Problems
Storm Slabs
Around 10 to 15 cm of snow is expected to accumulate Friday night, which will fall onto a weak layer of surface hoar crystals. The snow will likely form slab properties quickly, as it will fall with strong westerly wind. This is a recipe for storm slabs that could be likely to trigger and that could propagate far.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 22nd, 2020 5:00PM
