Avalanche Forecast
Issued: Jan 18th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Fresh slabs are expected to grow and become more sensitive as snow falls, the wind continues to blow, and the air temperature increases. There still remains a possibility of triggering a buried weak layer, particularly in the eastern and northern parts of the region.
Summary
Confidence
Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.
Weather Forecast
SATURDAY NIGHT: Cloudy with snowfall, accumulation 5 cm, moderate to strong southwest wind, alpine temperature -8 C, freezing level below valley bottom.
SUNDAY: Cloudy with snowfall, accumulation 5 to 15 cm, moderate to strong southwest wind, alpine temperature -6 C, freezing level rising to 700 m.
MONDAY: Increasing clouds with afternoon snowfall, accumulation 1 to 3 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1000 m.
TUESDAY: Cloudy with snowfall, accumulation 5 cm, light southeast wind, alpine temperature -6 C.
Avalanche Summary
A few wind slab avalanches were reported in the region on Friday at treeline and alpine elevations. They ranged from small (size 1) to large (size 2 to 3) and were triggered naturally and by humans. They most often occurred on northwest, north, and east aspects and had slab depths ranging from 15 to 80 cm.
Last weekend there were a few notable reports of large persistent slab avalanches in the Selkirks and the northern tip of the Monashees (near Blue River and Valemount). The avalanches failed on a 100 cm deep surface hoar layer on north and east aspects between elevations of 1200 to 2100 m. Observations suggest this layer has trended towards being less reactive. There is uncertainty on whether the layer will wake up with more snowfall and a rise in air temperature.
Snowpack Summary
Strong southwest wind and around 10 to 20 cm of new snow will form fresh storm slabs, with the most reactive slabs being in lee terrain features at higher elevations. The slabs may develop quickly due to relatively warm air temperature.
A layer of surface hoar is now buried 80-150 cm below the surface and could still be a concern in certain parts of the Selkriks and the northern end of the Monashees. A facet/crust layer from late November lingers near the bottom of the snowpack and has occasionally been reactive in isolated shallow snowpack areas.
Terrain and Travel
- Watch for fresh storm slabs building throughout the day.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
Problems
Storm Slabs
Around 10 to 20 cm of snowfall along with strong southwest wind and a warming trend will all work together to form new slabs. The slabs will be deepest and potentially touchiest in lee terrain features in exposed terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of surface hoar is buried 80 to 150 cm deep in the Selkirks and northern tip of the Monashees. As the air temperature rises, the likelihood of triggering this layer may increase. Use added caution in clearings around treeline during periods of warming.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Jan 19th, 2020 5:00PM
