Avalanche Forecast
Issued: Dec 25th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
Mark Herbison,
It's a tricky snowpack in many parts of the forecast region with a lot of variability with recent winds, snowfall and multiple weak layers.
There is a Special Avalanche Warning in effect. Click Here to access.
Happy Holidays!
Summary
Weather Forecast
Saturday will be cloudy with snow accumulations between 2-10cm over the region. The temperature inversion will dissipate as temps gradually get cooler over the next few days, ranging from -8 to -14. Winds will taper off Friday evening and remain light through the weekend. Cool temps, light winds and no snow in the 5 day forecast.
Snowpack Summary
Recent 25-45km/hr SW-W winds have blown the 30-60cm of snow from the past week into wind slabs at higher elevations. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 50cm and ~80 cm respectively. The decomposing Nov crust/facets sits at the bottom of the snowpack. Height of snow at tree line is 120-170cm.
Avalanche Summary
Four days of avalanche control this week produced mixed results, from no result to size 3.0. Most were storm slabs, sometimes stepping down to persistent layers.
Serac ice fall triggered a size 3.0 on Mt. Ball overnight on Thursday, most likely failing on the Nov 5 deep persistent layer.
Confidence
Problems
Wind Slabs
New wind slabs were formed from strong SW-W winds on Wed into Friday. These are mainly found in the alpine but have been reported at tree line as well.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
There are a variety of weaker layers down ~50-80cm depending on the area. These are the Dec 7 and 13th layers of facets, suncrust, and isolated surface hoar. Their reactivity is a bit sporadic but seems more reactive at tree line.
- Dig down to find and test weak layers before committing to a line.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
We have had a few observations of avalanches stepping down to the Nov. 5 crust and facets. This is a problem with higher uncertainty, and is most prevalent in shallow snowpack areas where the layer has weakened over time.
- Be cautious in shallow snowpack areas where triggering is more likely.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 26th, 2020 4:00PM
