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 Storm Slabs and Loose Wet.
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 to HIGH. 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 15-25/h km from the south and alpine temperatures + 9 degrees. Freezing levels 3500 m.
Thursday: A mix of sun and cloud. Ridgetop winds 10-20 km/hr from the southwest and alpine temperatures near + 4 degrees. Freezing levels 3000 m.
Friday: A mix of sun and cloud. Ridgetop winds 15-30 km/hr from the southwest and alpine temperatures + 5 degrees. Freezing levels 3000 m.
Avalanche Summary
On Tuesday afternoon numerous size 1-1.5 wet loose avalanches from steep south aspects were reported. A large natural avalanche size 2-2.5 from a north-facing alpine slope was also reported and likely occurred Monday night.Â
On Monday explosive triggered storm and wind slab avalanches were reported up to size 2.5. Crown depths generally ranged 20-50 cm, with a 120 cm deep crown observed in a heavily wind loaded feature.
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
Up to 25 cm of recent snow sits over a thin melt-freeze crust on south aspects and surface hoar in wind-sheltered areas around treeline. Fat pockets of wind loaded snow may be found in leeward features at upper elevations. Forecast sun and rising freezing levels into the alpine will have the greatest impact on the upper snowpack, showing signs of instability. and also promoting slab development.
The snowpack depth varies substantially with elevation. Below treeline 30 to 70 cm, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.
The mid to lower snowpack contains a series of crusts, the most notable of which is also the deepest, sitting just above the ground at elevations above 1500 m. This crust may have a thin overlying layer of weak faceted grains and/or surface hoar crystals, especially in sheltered areas around treeline. There is uncertainty as to whether these layer will be a concern going forward.Â
Terrain and Travel
- Extra caution for areas experiencing rapidly warming temperatures for the first time.
- Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
- Be cautious of buried obstacles especially below treeline.
Problems
Storm Slabs
A sharp rise in temperature coupled with solar radiation will promote rapid settlement and accelerated slab development in the recent storm snow. Be especially cautious where new snow may sit over a crust (south aspects) or surface hoar (wind sheltered areas around treeline).
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
A rapidly warming snow surface may release small loose wet avalanches, especially on steep sunny aspects. Pinwheeling is a good indicator of this type of instability.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 2nd, 2020 4:00PM
