Avalanche Forecast
Issued: Dec 3rd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Loose Wet.
swerner,
Avalanche Canada
Bump the avalanche danger to CONSIDERABLE in the alpine if the temperatures are well above zero degrees and the sun is shining.
Summary
Confidence
Low - Uncertainty is due to limitations in the field data.
Weather Forecast
It looks like the above freezing layer (AFL) will significantly weaken overnight with alpine temperatures dropping to 0 degrees. The AFL will strengthen through the day on Friday and Saturday likely leaving the region on Sunday.
Friday: Mostly cloudy and yet a strong alpine temperature inversion is forecast showing near +5 degrees. Ridgetop wind will be light from the southwest. Freezing levels 800 m.
Saturday: A mix of sunshine and some cloud cover. The inversion continues with an alpine high of +6 degrees. Ridgetop wind light from the south. Freezing levels near 1000 m.
Sunday: Sunny with some clouds. Alpine temperatures near 0 degrees with ridgetop wind light from the southwest. Freezing levels 1000 m.
Avalanche Summary
No recent avalanches reported on Thursday.
On Wednesday, numerous loose wet avalanches were reported from NE slopes above 2000 m. These avalanches were up to size 1.5 with no significant propagation.
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Snowpack Summary
Recent sun and warm air in the alpine likely had the greatest impact on the upper snowpack, showing signs of instability and promoting further slab development and cohesion. This may be most concerning where these slabs sit above an old thin crust (down 15 cm) on south aspects and feathery surface hoar crystals in wind-sheltered areas.Â
Northerly aspects will likely see fresh wind slab development at upper elevations on leeward slopes and melt-freeze conditions may exist on solar aspects at upper elevations. New surface hoar formation can be found mostly at treeline and below where it was protected from the warm temperatures, sunshine and wind.
Treeline snowpack depths sit around 50 to 80 cm in the south of the region.Â
Crusts from mid-and early-November are generally found 30 cm below the snow surface and 10 cm up from the ground at all elevations. While they are showing resistant planar results in snowpack tests, a lot of uncertainty still exists with limited observations.
Terrain and Travel
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
Problems
Wind Slabs
Recent wind from south to southwest has likely formed fresh wind slab at upper elevations in the immediate leeward side of slopes and terrain features. There may be some older wind slab lingering on southerly aspects so paying attention to clues while travelling is key.
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 some 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
Loose Wet
If the sun pokes out and alpine temperatures are above freezing wet loose avalanches may occur.
Aspects: South East, South, South West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 4th, 2020 4:00PM
