Avalanche Forecast
Issued: Dec 20th, 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.
jleblanc,
Avalanche Canada
Although wind slabs are the main concern, keep avoiding shallow areas at treeline, where a persistent slab can still be triggered.
Summary
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
An Arctic ridge of high pressure will continue to build from the Yukon into the B.C interior bringing clear skies and cold conditions across the province with outflow winds through Tuesday. Abundant moisture from the Pacific will invade the province starting on Wednesday morning.
MONDAY NIGHT: Clear skies / Strong northwest wind / Low of -16
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TUESDAY: Increasing cloudiness / Strong southwest wind / High of -13 / Snow starting in the evening 5-10 cm
WEDNESDAY: Snow, heavy at time 15-30 cm / Strong to extreme southwest wind / High -8
THURSDAY: Flurries 5 cm/ Moderate west wind / High of -12
Avalanche Summary
A widespread natural cycle of storm slabs were observed at all elevations/ aspects on most steep features during the last storm, including a few large wind slabs avalanches (size 2) as well as numerous loose dry avalanches up to size 1.5.Â
On Sunday, a skier-triggered size 2 was reported on a North aspect at 1850 m in the Monashee. This avalanche occurred on the early December crust/facet combo. The avalanche was triggered from a steep shallow rocky area beside a cliff feature.
If you go out, make sure to report any observations on the Mountain Information Network. Â
Snowpack Summary
Recent 20-35 cm of low-density snow can be found throughout the region, with significant amounts (up to 50 cm) in the northeast corner. Shifting winds have formed fresh wind slabs in isolated open areas at treeline and above. Many sluff were skier-triggered in low-density snow on steep slopes.Â
Below the new snow, the defining feature of the snowpack is a widespread crust that reaches as high as 2400 m and now sits 60-150 cm below the surface.Â
In some places, overlying snow is well-bonded to the crust but in others, weak faceted grains have been observed above it. The faceting is most prominent at treeline where the crust is thinner. The crust seems to begin to decompose, while snow profile tests are giving sporadic results.Â
Terrain and Travel
- Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- The best and safest riding will be on slopes that have soft snow without any slab properties.
Problems
Wind Slabs
20-35 cm + of low-density snow will remain available for wind transport throughout the day Tuesday, building reactive wind slabs on alpine features and open areas at treeline. Expected developing wind slabs on slopes that have not seen wind-affected snow during the last storm.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 60-150 cm near a crust layer that formed in early December. Although this persistent weak layer hasn't recently shown reactivity where it is buried one meter deep, there is still a potential for a high consequence scenario, if ever triggered. Avoid likely trigger spots such as steep, convex slopes, with a shallow or thin to thick snowpack, especially at treeline elevations.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2021 4:00PM
