Avalanche Forecast
Issued: Dec 1st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Loose Wet and Deep Persistent Slabs.
swerner,
Avalanche Canada
The snowpack doesn't respond well to rapid change. The impact of the afternoon sun and warm temperatures could bump up the avalanche danger in the alpine. Watch for signs of instability and be conservative with your terrain selection.
Summary
Confidence
Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
Wednesday: Sunny with some cloudy periods. Ridgetop winds light from the southwest and alpine temperatures + 5 degrees. Freezing levels 2500 m.
Thursday: A mix of sun and cloud. Ridgetop winds light and alpine temperatures near + 4 degrees. Freezing levels 3000 m.
Friday: A mix of sun and cloud. Ridgetop winds light and alpine temperatures + 2 degrees. Freezing levels 3200 m.
Avalanche Summary
No recent avalanche observations.
With sun and warming at upper elevations, I suspect we'll start to see some natural avalanche activity. Use extra caution with changing conditions.
Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!
Snowpack Summary
Wind and small inputs of snow have formed wind slabs on a variety of aspects at upper elevations. In more sheltered areas, recent snow may rest on a couple of layers of surface hoar 5-10 cm and 15-25 cm below the surface. Forecast sun and alpine temperature inversions may have the greatest impact on the upper snowpack, showing signs of instability. Snow surfaces may become moist and/ or wet when it's warm then re-freeze overnight.
Treeline snowpack depths sit around 100 to 150 cm in the north and 50 to 100 cm in the south of the region.Â
Melt-freeze crusts from mid-and early-November are generally found 30 cm below the snow surface and 30 cm up from the ground, respectively. While they are still showing results in snowpack tests, most reports indicate that the bonds at the interfaces with these crusts are improving.
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- Extra caution for areas experiencing rapidly warming temperatures for the first time.
- Be aware of the possibility for full depth avalanches due to deeply buried weak layers.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
Problems
Wind Slabs
Recent wind has varied from south to northwest so watch for old and new wind slabs on a variety of aspects, especially at ridge crests and on rollovers.
Aspects: North, North East, East, South East, South, South West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
A rapidly warming snow surface may release loose wet avalanches. Pinwheeling is a good indicator of this type of instability.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A crust exists near the base of the snowpack. A lack of decisive data on this layer is keeping it on our radar for now. While it's been showing results in snowpack tests in some areas, most reports describe an improving bond to the overlying snow. Potential for full depth avalanches may exist in areas where weak, sugary facets overly this crust, especially in areas of smooth ground cover such as scree slopes, grassy slopes, or rock slabs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 2nd, 2020 4:00PM
