Avalanche Forecast
Issued: Dec 29th, 2019 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is
cgarritty,
Avalanche Canada
Persistent slabs may be healing in parts of the Columbias, but this is not a mindset to carry with you in the Purcells. Snowpack structure here is fundamentally unstable and simply needs a trigger in the wrong place (like a shallow rocky start zone) to fail catastrophically.
Summary
Confidence
High -
Weather Forecast
Sunday night: Clear periods. Light variable winds.
Monday: Scattered cloud increasing overnight. Light northwest winds. Alpine high temperatures around -7.
Tuesday: Mostly cloudy with isolated flurries and a trace of new snow, continuing overnight. Light to moderate southwest winds. Alpine high temperatures around -7.
Wednesday: Mainly cloudy with isolated flurries bringing new snow totals to 5-15 cm . Light to moderate west winds. Alpine high temperatures around - 8.
Avalanche Summary
Recent avalanche activity in the Purcells has been simultaneously impressive and terrifying. Explosive control work in the central portion of the region continues to produce large persistent slab avalanches size 3 and larger on all aspects in alpine terrain. Explosives control missions continued to produce large persistent slab avalanches on Saturday.
Common characteristics of recent avalanches in the region include wide propagation, remote triggers and full depth avalanches scouring away the snowpack to ground. Natural avalanches of similar scale have been reported as recently as Friday.
Earlier in the week, there were several instances of large natural events taking out old timber beyond historical avalanche boundaries and running from the high alpine all the way to valley bottom.
Snowpack Summary
The Purcells received 60-120 cm from last weekend's big storm which has been settling into a slab over a couple of buried surface hoar layers 70-180 cm below the surface. This is normally a recipe for a concerning persistent slab avalanche problem in its own right, but the character of the lower snowpack complicates matters.
The base of the snowpack is astonishingly weak, much weaker than in an average season. This weakness is widespread across aspects and elevation bands, meaning it's almost everywhere. This basal layer consists of crust, facets and depth hoar. With the addition of the new snow last weekend, this weakness became overloaded and its failure has resulted in some spectacularly large and destructive avalanche activity.
Terrain and Travel
- Don't let the desire for deep powder pull you into high consequence terrain.
- Stick to simple terrain and be aware of what is above you at all times.
- Very large and destructive avalanches could reach valley bottom.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Valid until: Dec 30th, 2019 5:00PM
