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
Strong alpine wind will keep blowing all day Tuesday. Watch for changing conditions as wind slabs will become more reactive.
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 -15
TUESDAY: Increasing cloudiness / Strong southwest wind / High of -15 / Snow starting in the evening 5-15 cmÂ
WEDNESDAY: Snow heavy at times 20-30 cm / Strong to extreme southwest wind / High -8Â
THURSDAY: Flurries 5 cm/ Moderate west wind / High of -12
Avalanche Summary
A widespread natural cycle of storm slabs was observed at all elevations/ aspects after the last storm, including few very large storm slabs avalanches (size 2.5) as well as numerous loose dry avalanches up to size 1.5.Â
A naturally triggered size 2.5 persistent slab avalanche was observed in the Monashees on Wednesday on a West aspect at 2150 m. This avalanche failed on the early December facet/crust combo. It was 100 cm deep, a good example of the high consequence of triggering this layer.
If you go out, make sure to report any observations on the Mountain Information Network. Â
Snowpack Summary
30-40 cm of low-density snow can be found throughout the region, with significant amounts (up to 50 cm) in the southeast corner. Shifting winds have formed fresh wind slabs in isolated open areas at treeline and above. Many sluffs 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 2200 m and now sits 80-150 cm below the surface. In some places, overlying snow is well-bonded to the crust, but in others, weak faceted grains have been observed above it. The facets above the crust are most prominent at treeline where the crust is thinner. In areas where the crust is buried over a meter, it starts to decompose and show sporadic test results.
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 shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
- Seek out sheltered terrain where new snow hasn't been wind-affected.
Problems
Wind Slabs
30-45 cm + of recent snow will remain available for wind transport Tuesday, building reactive wind slabs on alpine features and open areas at treeline. Expect to see cross-loading on slopes that have not seen wind-affected snow during the previous storm.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 80-150 cm near a crust layer that formed in early December. Although this persistent weak layer has not shown recent reactivity where it is buried over a meter, it remains a low probability / high consequence scenario. Avoid likely trigger spots such as steep, convex slopes, with a shallow or thin to thick snowpack, especially at treeline.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2021 4:00PM
