Avalanche Forecast
Issued: Dec 13th, 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.
TRettie,
Avalanche Canada
Continually assess for changing snowpack conditions. Variable wind direction and the presence of a persistent weak layer make for challenging decision making. When in doubt choose conservative terrain.
Summary
Confidence
Weather Forecast
Monday night: 5cm of new snow expected with moderate Southeast winds. Low of -6 at 1600m.
Tuesday: up to 5cm of new snow with a high of -5 at 1600m. Winds will be light to moderate from the Southwest in the morning and from the West in the afternoon.
Wednesday: Trace amounts of new snow with moderate Southwest winds. High of -7 at 1600m.
Thursday: Up to 5cm of new snow with a high of -6 at 1600m. Winds becoming strong from the Northwest.
Avalanche Summary
On Saturday a skier controlled size 2.5 was reported in the Selkirks. This avalanche was on a East aspect at 2100m and ran on the early December crust/facet layer.
Wind slabs up to size 2 were reactive to ski cuts and explosives on Sunday. A limited natural avalanche cycle up to size 2.5 was reported to have run during the storm on Saturday.
Snowpack Summary
15-30 cm of recent snow has seen redistribution by strong wind at upper elevations.
The defining feature of the snowpack is a prominent and widespread crust that reaches as high as 2400 m in the alpine now sits 40-70 cm below the surface. In many places, overlying snow is well-bonded to the crust but in others, weak faceted grains have been observed growing above it around treeline. Snowpack models show the faceting process progressing quickly at this elevation, likely due to the amount of heat and moisture trapped by the crust. We will be closely monitoring this layer going forward. The snowpack structure is relatively simple beneath the crust, with treeline snow depths around 100-200 cm.
Terrain and Travel
- Approach lee and cross-loaded slopes with caution.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Wind Slabs
Small inputs of new snow will continue to feed wind slabs. As wind direction shifts southeast on Monday, watch for changes in loading patterns.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
40-70 cm of snow sits over a weak layer on a thick crust. While only a handful of avalanches have been reported to have run on this layer, they have been large. Avalanches on this layer may be triggered by humans or vehicles from thin spots or by large loads like wind slab avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 14th, 2021 4:00PM
