Avalanche Forecast
Issued: Jan 8th, 2020 4:30PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
astclair,
Avalanche Canada
Although snowfall has tapered, avalanche conditions remain complicated and dangerous. Stick with conservative terrain choices and give the snowpack time to adjust.
Summary
Confidence
Weather Forecast
Wednesday night: Clearing overnight, light northwest wind, alpine temperature -16 C.
Thursday: Mostly cloudy, isolated flurries with trace accumulations, light west wind, alpine high temperature -12 C.
Friday: Cloudy, 5-15 cm of snow, strong south wind, alpine high temperature -10 C.
Saturday: Cloudy, 5-15 cm of snow, moderate southwest wind, alpine high temperature -14 C.
Avalanche Summary
There have been numerous reports of large (size 2-2.5) avalanches from both natural and human triggers on a variety of aspects and elevations releasing on a surface hoar layer formed in late December. These avalanches have been breaking 60-120 cm deep. Several of them have been remote-triggered, like the one in this MIN from Wednesday.
Be sure to check out this MIN, this MIN, and this MIN for helpful illustrations of slopes that are likely to harbor this problem. A sincere thanks to the community for submitting these reports!
As the new snow settles, storm slab avalanches will remain possible trigger, and they will have the potential to step down to this deeper weak layer, forming very large and destructive avalanches.
Snowpack Summary
The most recent storm delivered 15-35 cm of snow across the region with moderate to strong southwest winds. Higher accumulations fell in the southern and eastern parts of the region. Expect storm slabs to be especially touchy in lee terrain features where southwest winds have been drifting new snow into stiffer, more reactive slabs.
A very concerning layer of surface hoar from late December is now buried 60-120 cm deep. This layer formed in late December and continues to produce large avalanches across aspects and elevations. Recent snowpack tests have confirmed this weak layer's propagation potential.
Terrain and Travel
- The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Choose simple, low-angle, well supported terrain without convexities.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
The most recent storm delivered 15-35 cm of snow across the region forming reactive storm slabs. With moderate to strong southwest winds, storm slabs will be more pronounced in lee terrain features at higher elevations. There is potential for storm slabs to step down to deeper weak layers, forming large and destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A concerning layer of surface hoar from late December is now buried 60-120 cm deep. This layer has produced many large avalanches across aspects and elevations with incremental loading from new snow and wind. A few of these avalanches were human-triggered remotely from adjacent slopes. This problem warrants conservative margins with terrain decisions.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 9th, 2020 5:00PM
