Avalanche Forecast
Issued: Jan 21st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
ahanna,
Avalanche Canada
Where windslabs sit over weak sugary facets, windslab avalanches will likely remain sensitive to human triggering. Use caution around convexities near treeline.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
Tuesday night: Mostly cloudy with isolated flurries bringing up to 5 cm of new snow. Light southwest winds. Alpine low -6 C.
Wednesday: Mostly cloudy with isolated flurries bringing a trace of new snow. Light southwest winds. Alpine high -4 C. Freezing level rising to 700 m in the evening.
Thursday: Mostly cloudy with scattered flurries bringing 5-10 cm of new snow. Moderate to strong southwest winds. Alpine high -5 C. Freezing level around 500 m.
Friday: Mix of sun and cloud with scattered flurries bringing up to 5 cm of new snow. Moderate to strong southwest winds. Alpine high -3 C. Freezing level around 600 m.
Avalanche Summary
Windslab avalanches, skier triggered size 1.5 and natural size 2.5 were observed in the Howson ranges Monday.
Over the weekend, a natural storm cycle was observed at treeline and below. Slabs were soft and thin but propagated widely resulting in avalanches up to size 2. They ran on the faceted interface buried January 17th.
There have been reports trickling in over the past month of natural persistent slab avalanches up to size 3 in the Bulkley Valley. These are thought to have been failing on the November crust/facet layer near the ground. The last reported activity at this interface was Monday January 13th.Â
Snowpack Summary
Extensive wind effect at all elevations is well illustrated in photos from this MIN post from Saturday. Southerly winds are forming fresh windslabs from 10-20 cm (up to 50 cm in the Howson area) of recent snow in places that were previously scoured by northeasterly arctic outflows. In wind sheltered areas at treeline and below, the recent snow sits on a layer of touchy facets.
A layer of surface hoar up to 1 m in depth may also be found at treeline. A deep crust/facet layer lurks at the base of the snowpack. A couple of large avalanches are suspected to have run on this interface in the last few weeks. These larger avalanches have been specific to lee and cross-loaded features in the alpine.
Terrain and Travel
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
Problems
Wind Slabs
Recent southerly winds redistributed 10-20 cm of recent snow into windslabs in places that were previously scoured by northeasterly arctic outflows. In areas sheltered from the northeast wind event, the recent snow sits over weak, sugary facets and will likely continue to be reactive to human triggering at this interface.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 22nd, 2020 5:00PM
