Avalanche Forecast
Regions: Cariboos.
Expect touchy avalanche conditions at all elevations. Wind-kissed storm slabs have potential to propagate widely and loose dry avalanches are likely on steep, sheltered slopes.
In northern areas that received less than 20 cm from this storm, avalanche danger may be a step lower.
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
Highest snowfall amounts are forecast for the south of the region in the mountains near Williams Lake, Clearwater and Blue River.
Sunday night: Snowfall 5-15 cm, moderate SW wind, treeline temperature around -8 °C.
Monday: Isolated flurries up to 3 cm, light to moderate NW wind, treeline high around -10 °C.
Tuesday: Mainly sunny, light to moderate NW wind, treeline high around -15 °C.
Wednesday: Mostly cloudy, moderate SW wind, treeline high around -18 °C.
Avalanche Summary
The theme during the dry spell last week was large cornice failures and wind slab avalanches size 2-3 in the alpine. Last Sunday, a snowmobiler accidentally triggered a large wind slab (size 2.5) on a lee alpine slope. The fracture line was up to 1 m deep.
A deep persistent avalanche problem in the North Columbia forecast region has produced large and notable avalanches during periods of changing weather. And the southeast corner of the Cariboos appears to have a similar lingering problem. Last weekend, explosives triggered a 2.5 deep persistent avalanche on a NE aspect at 2100 m south of Valemount.
Snowpack Summary
New snow continues to accumulate over faceting wind affected surfaces in the alpine, a melt-freeze crust on steep solar aspects & low elevations and a widespread layer of large surface hoar crystals. New snow is expected to adhere poorly at this interface.
There are three prominent layers in the upper snowpack which have been largely dormant during the dry spell but may become reactive with new snow loads. These include a thin crust and a spotty layer of surface hoar down 20 cm, a layer of facets and small surface hoar around 60 cm deep, and a thick layer of facets from the end of December 80-100 cm deep.
The lower snowpack is strong and settled in most parts of the region, except the southernmost part of the region around Blue River where there is a deeply buried crust/facet layer from early December that could be exhibiting similar behavior to the deep persistent slab problem in the neighboring North Columbia region. This layer is most prevalent at below treeline elevations and has been reactive to heavy triggers like smaller slab avalanches that step down. Check out our latest forecaster blog on the crust that never dies.
Terrain and Travel
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Avoid freshly wind loaded terrain features.
- The trees are not a safe haven right now.
- Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
- Good day to make conservative terrain choices.
Avalanche Problems
Storm Slabs
New snow is is adhering poorly to previous surfaces, especially where it sits over surface hoar or a crust. As a result, storm slabs are touchy and have potential for wide propagation.
Loose dry avalanches run easily in wind sheltered areas where the snow hasn't formed a slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Almost Certain
Expected Size: 1 - 2
Persistent Slabs
We have uncertainty around residual reactivity of a few layers in the upper snowpack which have been largely dormant during the dry spell but may become reactive with new snow loads. These layers are detailed in the second paragraph of the snowpack summary.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 2 - 3