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 and Deep Persistent Slabs.
mconlan,
Avalanche Canada
Friday night's storm will drop snow onto various surfaces that the snow may not bond well to. Conservative decision making is recommended. The danger may be one step lower in the south of the region (e.g. Coquihalla, Manning), where less snowfall is forecast.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 to 15 cm in the north of the region and 5 cm in the south, moderate to strong west wind, alpine temperature -6 C, freezing level 1000 m.
SATURDAY: Mix of sun and cloud, light to moderate northwest wind, alpine temperature -8 C, freezing level 1000 m.
SUNDAY: Cloudy with snowfall, accumulation 5 cm, moderate southwest wind, alpine temperature -7 C, freezing level 800 m.
MONDAY: Morning snowfall and afternoon clearing, accumulation 5 cm, light to moderate west wind, alpine temperature -10 C, freezing level 700 m.
Avalanche Summary
No new avalanches were observed on Thursday. Avalanche activity is expected to increase Friday night into Saturday with the new snow, particularly in the north of the region.
Snowpack Summary
Around 5 to 15 cm of snow is expected to fall Friday night, with the most in the north of the region. The snow will fall onto a melt-freeze crust on solar aspects or a weak layer of surface hoar, which was reported to be 4 to 8 mm in size in sheltered terrain. In the north of the region, the surface hoar sits on about 10 to 15 cm of weak and sugary near-surface facets. Friday night's snow will also fall with strong westerly wind, so the deepest deposits will be in lee terrain features.
The midpack is well-settled.
In the north part of the region (e.g. Duffey/Hurley/Goldbridge), a deep instability exist in the snowpack, consisting of a weak basal facet-crust complex. Sporadic avalanche activity on this layer is keeping it on our radar, with the latest report described here. In the south of the region, including the Coquihalla and Manning areas, there are no concerns about deeply buried weak layers.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
- Choose conservative terrain and watch for clues of instability.
Problems
Storm Slabs
Snowfall Friday night may not bond well to underlying layers of weak surface hoar crystals, faceted grains, or a melt-freeze crust. The most snow is forecast in the northern half of the region, where upwards of 15 cm may accumulate. The southern half of the region may only see 5 cm. Nonetheless, the snow will fall with strong westerly wind, so slabs will be thicker and potentially touchier in lee terrain features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
In the north of the region (e.g. Duffey, Hurley, Goldbridge), a buried weak layer lingers in the snowpack. The most likely place to trigger this layer is in shallow and rocky terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 22nd, 2020 5:00PM
