Thin, soft slabs from recent snowfall will likely continue to be reactive to human triggering, especially in wind sheltered areas at and below treeline where they sit over weak facets.
|Tue, 21 Jan||Wed, 22 Jan||Thu, 23 Jan|
|Alpine||2 Moderate||2 Moderate||2 Moderate|
|Treeline||2 Moderate||2 Moderate||2 Moderate|
|Below Treeline||1 Low||1 Low||1 Low|
- Uncertainty is due to the limited number of field observations.
Travel and Terrain Advice
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Watch for areas of hard wind slab on alpine features.
- Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
- Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
Southerly winds are forming fresh windslabs from 10-20 cm of recent snow in places that were previously scoured by northeasterly arctic outflows.
Deep Persistent Slab
A deep facet/crust layer from November lurks at the base of the snowpack. It has produced infrequent but very large avalanches in lee and cross-loaded alpine terrain.
Over the weekend, a natural storm cycle was observed in the Howson ranges, 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.
As recently as Saturday, we have received reports of windslab avalanches size 1.5-2.5 mostly around treeline. Crown depths have been up to 1 m, running on a layer of surface hoar layer buried on January 10th.
There have been reports trickling in 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.
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 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.
Monday night: Mostly cloudy with isolated flurries bringing a trace of new snow. Light southwest winds. Alpine low -7 C.
Tuesday: Mostly cloudy with isolated flurries bringing a trace of new snow. Moderate southeast winds. Alpine high -6 C.
Wednesday: Mix of sun and cloud with isolated flurries bringing a trace of new snow. Moderate south to southwest winds, strong at ridgetop. Alpine high -8 C.
Thursday: Mostly cloudy with scattered flurries bringing up to 5 cm overnight followed by 5 cm over the day. Moderate southwest winds, strong at ridgetop. Alpine high -5 C.