Avalanche Forecast
Issued: Dec 29th, 2021 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
JSmith,
Avalanche Canada
Conditions in this region are "Tricky" right now. Numerous very large persistent slab avalanches failing on a crust have been reported in recent days. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
WEDNESDAY NIGHT: Mostly cloudy / Moderate west wind / Low of -22
THURSDAY: Mix of sun and cloud / Light northwest wind / High of -16
FRIDAY: Sunny / Light northwest wind / High of -17
SATURDAY: Mix of sun and cloud / Strong northwest wind / High of -17
Avalanche Summary
A naturally triggered size 3 persistent slab was reported near Rossland on Wednesday. See MIN.
Explosive control work at Kootenay Pass on Tuesday produced numerous persistent slab avalanches failing on the early December crust, up to size 3.5.
A rider triggered size 2.5 persistent slab avalanche involving several riders was reported near Nelson on Monday. The avalanche occurred on a southeast aspect at approximately 1900 m. It failed on the crust formed in early December. The treeline slope was heavily wind effected and the rider triggered the avalanche from a thin spot where the layer was only around 60 cm deep. There is a MIN report of the incident.
Additionally, several natural and human triggered storm slab avalanches up to size 2.5 were reported on all aspects and elevations on Monday. An example of a skier triggered storm slab near Rossland can be found in a MIN report HERE.
Snowpack Summary
Recent storm totals reached over 100 cm. There is a lot of snow available for transport which will form fresh wind slabs when wind speeds increase to moderate.
A crust formed in early December has been responsible for numerous very large persistent slab avalanches in recent days. The depth of the crust ranges widely from 50-150 cm and is most likely to be triggered in wind affected terrain below ridgetops.Â
Nearly all of the recent avalanches have been triggered from shallow spots in the snowpack where the crust is less than 100 cm deep. Avoid steep, rocky slopes with a shallow or thin to thick snowpack.
The lower snowpack is composed of several early-season crusts. Snow depths at treeline average 150-300 cm.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
Problems
Wind Slabs
Forecast westerly wind Wednesday night may form fresh wind slabs reactive to human triggers. Look for signs of instability: whumpfing, hollow sounds, shooting cracks, and recent avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A persistent slab problem formed by a crust down 50-150 cm has created a low likelihood, high consequence scenario that is difficult to forecast. This layer is most likely to be triggered in windy areas where the depth of the snowpack is highly variable.
Avoid likely trigger spots such as steep, rocky or convex slopes with a shallow or thin to thick snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 30th, 2021 3:00PM
