Avalanche Forecast
Issued: Dec 16th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
trettie,
Avalanche Canada
As the temperatures drop over the next 48 hours you should be planning on dialing things back. Even a small accident can have big consequences with cold temps and short days.
We have uncertainty around the reactivity of a buried weak layer that produced large rider-triggered avalanches last weekend. Read our latest blog for advice on how to manage a persistent slab problem.
Summary
Confidence
Avalanche Summary
On Thursday explosive control produced wind slab avalanches up to size 1.5 on north aspects.
Persistent slab activity has died down over the past couple days but over the last weekend the mid November layer was sensitive to rider triggering.
In the neighboring central Columbia and Kootenay Boundary regions, where it is buried deeper, this layer has produced Larger rider-triggered avalanches. Unfortunately, more likely than not, this is a sign of what is to come for the Purcells.
Snowpack Summary
Variable surfaces range from hard old wind slabs in exposed features at upper elevations to soft, unconsolidated facets in sheltered areas. As the winds shift to the northwest new wind slabs could form on southerly and easterly aspects.
A concerning weak layer composed of surface hoar, facets and/or a crust that formed in mid November is now buried 15-40 cm deep. Avalanche activity has been observed on this layer and is expected to continue as the overlying snow takes on more slab character due to settlement, wind and additional snow load.
Alpine snowpack distribution is variable, with depths ranging from 40 to 140 cm.
Weather Summary
Friday Night
Cloudy with the possibility of light flurries bringing trace amounts of new snow. Moderate westerly winds with a low of -15 at 1800m.
Saturday
Scattered flurries bringing up to 5cm of new snow. Light to moderate westerly wind. High of -14 at 1800m.
Sunday
Scattered flurries bringing up to 5cm of new snow. Light to moderate southerly wind. High of -18 at 1800m.
Monday
A mix of sun and cloud with no new snow expected. Light southwest winds and a high of -22 at 1800m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- In times of uncertainty conservative terrain choices are our best defense.
Problems
Persistent Slabs
A layer of surface hoar, facets and a crust from mid november is buried around 50cm deep but can be found down as much as 80cm. This layer is most likely to be rider triggerable on slopes at treeline where the snow above feels stiff and consolidated. Avalanche activity on this layer has been decreasing over the week but it's not going anywhere so keep this in mind as you move through terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Northwest winds have likely redistributed snow. forming wind slab on southerly and easterly aspects and cross loaded others. New wind slabs could be more reactive where they overlie facets .
Aging wind slabs formed by previous southwest wind may remain reactive to human triggers, especially where they overlie a weak, sugary lower snowpack.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 17th, 2022 4:00PM
