Avalanche Forecast
Issued: Dec 25th, 2019 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
cgarritty,
Avalanche Canada
Several weak layers are active in the snowpack. Successfully managing their complexity is less about picking out the most problematic layer and more about sticking to diligent group management and more conservative terrain while the snowpack strengthens.
Summary
Confidence
Weather Forecast
Wednesday night: Clear periods. Light variable winds.
Thursday: A mix of sun and cloud with cloud increasing over the day. Light to moderate southwest winds increasing over the day. Alpine high temperatures around -8.
Friday: Mainly cloudy. Light to moderate southwest winds shifting northwest. Alpine high temperatures around -8.
Saturday: Mainly cloudy. Light to moderate southwest winds. Alpine high temperatures around -10.
Avalanche Summary
Several more large persistent slabs were triggered with explosives control in the Nelson area on Monday. These slabs featured crown depths of 15-120 cm, giving some evidence of wind loading. These avalanches are suspected to have released on our early November facet/crust layer, which exists below two other persistent weak layers of concern.
A widespread avalanche cycle occurred on Saturday, with observations of large artificially triggered avalanches continuing into Sunday. Many of these recent avalanches released within the storm snow, and large avalanches weren observed on all aspects, generally above 2000 m. Numerous other large to very large avalanches were also triggered by explosives on the late-November layer described in our Snowpack Summary.
Snowpack Summary
The stormy period that ended early this week saw around 70 to 100 cm of snow deposited in the region, initially accompanied by strong west wind. This snow has loaded multiple weak layers, including:
- a feathery surface hoar layer now buried around 70 to 110 cm.
- an older surface hoar layer buried about 90 to 130 cm, associated with a melt-freeze crust on steep south aspects.
- a complex layer of weak and sugary faceted snow, surface hoar, and melt-freeze crusts in the bottom half of the snowpack, buried in late November.
There is uncertainty on which of these layers will emerge as our primary persistent slab problem. However, given extensive recent avalanche activity during and in the days after the storm, it remains prudent to make terrain decisions with the understanding that any one of these deeply buried layers could produce large and destructive avalanches with a human trigger.
Terrain and Travel
- Don't let the desire for deep powder pull you into high consequence terrain.
- Make conservative terrain choices and avoid overhead hazard.
Problems
Persistent Slabs
Several different weak layers can be found in the snowpack, they are now deeply buried, and they have produced large avalanches as recently as Monday. It remains prudent to assume these layers are present, reactive to human triggers, and capable of forming very large, destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 26th, 2019 5:00PM
