Avalanche Forecast
Issued: Dec 16th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
swerner,
Avalanche Canada
Wind slabs are likely reaching threshold and could be reactive to human triggers. Choose conservative terrain and watch for signs of instability such as whumphing, cracking and recent avalanches.
Summary
Confidence
Weather Forecast
Wednesday Night: Snow amounts 5-10 cm with ridgetop wind strong from the southwest. Freezing levels valley bottom. Ridgetop winds 40-70 Km/hr from the southwest.
Thursday: Cloudy with some sunny periods. Snow amounts generally light through the day. Ridgetop wind 45-85Km/hr. from the southwest.
Friday: Light amounts developing through the day and overnight. Ridgetop wind 55-85Km/hr from the southwest.
Saturday: Snow through the day near 10 cm with rising freezing levels to 1600 m. Winds continue to blow 35-95Km/hr.
Avalanche Summary
No new avalanches to report on Wednesday, but visibility was poor due to clouds and blowing snow.
Wind slabs may be reactive on Thursday at treeline and above.
Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter.
Snowpack Summary
10- 20 cm of new snow and strong to extreme ridgetop wind from the southwest is forecast for the rest of the week along with a bit of new snow. New and reactive wind slabs will likely build at treeline and in the alpine.
Currently, 30-50 cm of snow from last week overlies a hard melt-freeze crust formed in early December at least up to 2000 m. To date, this layer has not been an avalanche concern but by Thursday it may reach its tipping point and that concern and hazard will likely increase with snow/wind load and rising freezing levels. Use caution if you find cohesive snow above the crust, particularly if there are weak, sugary faceted grains immediately above or below the crust.
The snowpack depth varies substantially in the region and has been described as thin, wind-hammered, variable, and tapering rapidly at lower elevations. The average snowpack depth at treeline is approximately 100 cm.
The middle of the snowpack has been reported as being well-consolidated and may host another hard melt-freeze crust.
The base of the snowpack consists of a hard melt-freeze crust from early-November that may have faceted grains around it. There has not been recent avalanche activity on this layer but it remains on our radar. The most likely spot to trigger it would be on thin and rocky slopes.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid areas where the snow feels stiff and/or slabby.
Problems
Wind Slabs
Strong southwest wind is forecast for the rest of the week along with a bit of new snow. Use caution near ridges and avoid leeward slopes, particularly where you find stiff wind affected snow. Loose-dry sluffing from steep terrain features.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
30-50 cm of snow currently sits above a buried crust from early December. A cohesive slab will likely exist with forecast snow, strong wind, and warming. Sugary, facets above and/or below the crust may weaken the bond and the persistent slab may become reactive, especially to human triggers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 17th, 2020 4:00PM
