Avalanche Forecast
Issued: Dec 10th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
swerner,
Avalanche Canada
The recent 10-20 cm of new snow has a poor bond to the underlying crust. Pockets of stiff wind slab may be reactive to human triggers at treeline and in the alpine, especially on leeward slopes and behind terrain features.
Summary
Confidence
Moderate - Uncertainty is due to limitations in the field data. Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
High pressure mostly dominates with some clouds and the chance of flurries on Friday then sunshine and cool temperatures for the weekend. Sunday evening should see the next change with possible snow forecast. Alpine temperatures will be near -10 and freezing levels will be in the valley bottom. Ridgetop winds will generally be moderate from the south-southwest through the forecast period.
Avalanche Summary
On Thursday, natural wind slab avalanches were reported up to size 2. The recent storm snow is not bonding well to the underlying crust. Wind slabs may be reactive to rider triggers at treeline and above on Friday.
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Snowpack Summary
10- 20 cm of recent snow fell at upper elevations while the rest of the precipitation came in as rain or freezing rain. Recent reports suggest that the freezing rain occurred from 1800m to 2000m “ish†with rain at lower elevations which may have destroyed the surface hoar at 2000m and below. All elevations are now hosting a burley crust under the new snow.
Up high, stiff wind slab exists on leeward slopes where the new snow deposits into deeper drifts, especially where the new snow sits above this recent rain/freezing rain crust, or the older melt-freeze crust found on solar aspects. Digging deeper in the snowpack two crusts exist from November. One down approximately 30 cm, just below the old surface hoar, and the other sits deeper (down 70-90 cm) and is widespread up to 2500 m. The deeper crust seems to be bridged by a well-consolidated mid-pack in most areas. These crusts have shown no recent reactivity in snowpack testing but remain on our radar moving forward.
The snowpack is generally thin, wind hammered, variable in wind-scoured areas, and tapers rapidly at lower elevations. Snowpack depths at sheltered upper treeline elevations are nearing 100 cm and beginning to exceed the threshold for avalanches.
Terrain and Travel
- Avoid areas where the snow feels stiff and/or slabby.
- A crust on the surface will help bind the snow together, but may make for tough travel conditions.
- Closely monitor how the new snow is bonding to the crust.
Problems
Wind Slabs
The recent snow has a poor bond to the underlying crust. Isolated pockets of stiff wind slab could be reactive to human triggers especially where it sits on a widespread crust. Loose-dry sluffing may be seen from steeper slopes and terrain features.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 11th, 2020 4:00PM
