Avalanche Forecast
Issued: Dec 24th, 2019 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ghelgeson,
Avalanche Canada
Considerable avalanche hazard means that human triggered avalanches are likely, and this is exactly the situation right now. Very large recent avalanches have had crowns up to 200 cm in depth. Anything besides non avalanche terrain, or simple terrain is out of the question.
Summary
Confidence
Weather Forecast
We’re entering a rather quiet weather period with coolish temps and no significant snowfall expected, at least through boxing day. The region should see winds pick up later in the week and there is potential for a small shot of snow Thursday night, and then another one Saturday Night.
CHRISTMAS EVE: Freezing level at valley bottom, light variable wind, no significant precipitation expected.
CHRISTMAS: Scattered cloud cover with clearing expected after lunch, freezing level at valley bottom, light northwest wind, no significant precipitation expected.
BOXING DAY: A few clouds in the morning, cloud cover building to broken by sundown, freezing level at valley bottom, moderate to strong south/southwest wind, trace of snow possible during the day, potential for 5 to 10 cm by Friday morning.
FRIDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong west/southwest wind, trace of snow possible during the day.
Avalanche Summary
The recent storm was a significant one, and there is a great deal of uncertainty at this time as to how quickly the snowpack will gain strength. Avalanche occurrences are tapering, but recent avalanches have been very large. Patience and conservative terrain selection is the best way to manage this uncertainty.
On Monday natural avalanche activity from size 2 to 3 was observed on a variety of aspects above 2100 m. Control work produced avalanches from size 2 to 4 that involved all elevation bands, some mature timber was taken out by very large avalanches.
On Sunday, there were dozens of reports of natural, human and explosives triggered avalanches up to size 4. These were a mix of storm slab and persistent slab avalanches.
On Thursday, Friday and Saturday, there were numerous reports of natural, human and explosives triggered avalanches up to size 3.5. A number of these were triggered remotely.
Snowpack Summary
The North Columbias received upwards of 80 cm between Thursday night and Saturday night. Storm slabs are likely widespread and may still be reactive to human triggers.
There is anywhere from 100-160 cm of snow on top of a widespread layer of large, feathery surface hoar crystals. This layer has reportedly been responsible for numerous recent avalanches and may be reactive to human triggers.
A weak layer that formed in late November is now over 170 cm deep. This is the layer of concern relating to the persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect
Terrain and Travel
- Make conservative terrain choices and avoid overhead hazard.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Storm Slabs
Storm slabs could still be triggered by humans, especially in wind loaded areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
There is a weak layer of surface hoar down 100-160 cm. Numerous recent avalanches have occurred on this layer and human triggering is a possibility.
Another weak layer that formed in late November is now down over 170 cm. This layer could be triggered from shallow snowpack areas, and it is also possible for avalanches triggered on the shallower layer to step down to this layer, resulting in very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 25th, 2019 5:00PM
