Avalanche Forecast
Issued: Dec 20th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
kdevine,
Avalanche Canada
Fresh storm slabs will likely be reactive to human triggering. Choose conservative terrain, avoid exposure to avalanche terrain from above and watch for signs of instability such as whumphing, cracking and recent avalanches.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
FRIDAY NIGHT - Cloudy with scattered flurries, up to 5 cm / southwest wind, 20-30 km/h / alpine low temperature near -7
SATURDAY - Cloudy with flurries, 5-10 cm / southwest wind, 20-30 km/h / alpine high temperature near -6
SUNDAY - Cloudy with sunny periods / southeast wind, 20-30 km/h / alpine high temperature near -10
MONDAY - A mix of sun and cloud / northwest wind, 10-20km/h / alpine high temperature near -9
Avalanche Summary
There is a notable weak layer of surface hoar that is down 60-100 cm and there is some uncertainty as to how reactive this layer may be to human triggers. Treat this layer with caution and choose conservative terrain to manage this uncertainty.
On Friday, there were a few reports of natural and human triggered avalanches. Check out this great MIN report from Allan Creek that outlines reactive storm slab conditions.
Heavy snowfall earlier in the week likely resulted in a cycle of natural avalanches on Tuesday and Wednesday, leaving storm slabs very reactive to human triggering. Observations were limited on Tuesday and Wednesday due to poor visibility.
Snowpack Summary
A continuous wave of storms has delivered anywhere from 35-70 cm of snow to the Cariboos over the past week. Some areas have seen as much as 40 cm since Thursday night, and another 5-10 cm is expected during the day on Saturday. Storm slabs are expected to be widespread and reactive in areas that received more than 20 cm since Thursday.
60-100 cm of snow now sits above a widespread layer of feathery surface hoar crystals. This layer has been responsible for several recent human triggered avalanches in the region. There is some uncertainty as to whether or not this layer will gain strength in the near future and so it should be treated with caution.
A weak layer formed in late November is now buried around 1 m or more below the surface. 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. Below this, a variety of crusts from late October are buried deeper in the snowpack.
Terrain and Travel
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Make conservative terrain choices and avoid overhead hazard.
Problems
Storm Slabs
Continuous snowfall and strong wind has formed touchy storm slabs. Human triggered avalanches are likely.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A couple of weak layers formed in late November and early December are now sitting about 1 m below the surface.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 21st, 2019 5:00PM
