Avalanche Forecast
Issued: Jan 18th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Freshly formed wind slabs and concern for buried weak layers are keeping danger ratings elevated. Put your guard up around steep openings in the trees and keep it raised if you reach the alpine, where wind slabs and deeper snowpack weakness remains in play.
Summary
Confidence
Avalanche Summary
On Tuesday, a small skier-triggered persistent slab avalanche was reported near Kispiox. This avalanche occurred at treeline and failed on a weak layer of surface hoar sitting on a firm wind-packed surface. Several natural wind slab avalanches were also observed throughout the region, mainly in the alpine (size 1-2).
Looking forward to Thursday, wind and snowfall will continue to form fresh wind slabs. Avoid wind-loaded areas at upper elevations and keep in mind the potential for deeper instabilities to produce large and surprising avalanches.
Snowpack Summary
Continued snowfall will add to 20-40 cm of recent storm snow. At upper elevations, southerly winds are scouring windward areas and redistributing this storm snow into wind slabs in lee areas.
Several persistent weak layers may be found in the top meter of the snowpack. Most prominently, a layer of surface hoar buried in early January is now 20-50 cm deep. A weak layer of facets and/or surface hoar buried in late December is now down 70-110 cm.
In alpine terrain, triggering one of these layers is most likely on steep rocky slopes where they present as facets. In treeline terrain, the layers are most likely triggered on steep slopes in open trees where they present as preserved surface hoar.
In the north of the region, the lower snowpack remains weak and heavily faceted.
Weather Summary
Wednesday night
Cloudy with clear periods and isolated flurries, trace to 5 cm accumulation. Alpine temperatures drop to a low of -9 °C. Ridge wind southwest 25 km/h gusting to 65 km/h. Freezing level at valley bottom.
Thursday
Cloudy with snowfall, 5 of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 30 km/h gusting to 75 km/h. Freezing level 400 metres.
FridayCloudy with rain/snow, 5-10 cm of new snow accumulation at higher elevations. Alpine temperatures reach a high of 0 °C. Ridge wind southwest 35 km/h gusting to 90 km/h. Freezing level 1400 metres.
SaturdayFlurries, 5 cm of accumulation. Alpine temperatures reach a high of -7 °C. Ridge wind southwest 30 km/h gusting to 70 km/h. Freezing level 700 metres.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Problems
Wind Slabs
Continuing southerly winds and new snow will form fresh wind slabs in alpine and treeline lees. Watch for changing conditions with aspect and elevation and avoid wind-loaded areas.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Triggering persistent slab avalanches remains possible due to several weak layers in the top metre of the snowpack. Facet layers are the primary concern in alpine terrain, while preserved surface hoar layers are the concern in treeline terrain.
In the north of the region, the lower snowpack remains weak and heavily faceted. Large triggers such as cornice failure or smaller avalanches stepping down to this layer are possible.
Avalanches that start as wind slabs may step down to these deeper layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 19th, 2023 4:00PM
