20-30 cm of recent snow accompanied by strong to extreme wind has formed reactive storm slabs and wind slabs. Natural avalanche activity may taper off on Friday but skier and rider triggering is likely.
Fresh and reactive wind slabs will build throughout the day.
Cranking southwest wind and new snow have formed fresh new wind slabs. Changing winds from the northwest on Friday will add to the complex loading pattern. Wind slabs may be found on most aspects at upper elevations.
20-30 cm of new snow fell by Thursday afternoon, forming new storm slabs. The wind is forecast to howl from the southwest to northwest, so wind slabs will rapidly build at treeline and alpine elevations as well. Including the weekend's snow, around 40 to 80 cm of recent storm snow will have built above the surfaces formed mid-February, potentially including weak surface hoar and/or faceted grains. These slabs will remain likely for riders to trigger on Thursday. Should 25 cm or more snow accumulate, another natural avalanche cycle may occur on Thursday.
Friday: A mix of sun and cloud with alpine temperatures near -10. Ridgetop wind strong from the northwest. Freezing level valley bottom.
Saturday: Cloudy with sunny periods and flurries. Alpine temperatures near -8. Ridgetop wind strong from the West and freezing level valley bottom.
Sunday: Snow 10-20 cm. Alpine temperatures near -5 and ridgetop wind strong to extreme from the southwest. Freezing level 900 m.
No recent reports by Thursday afternoon, but I suspect a natural avalanche cycle may have occurred.
We are still receiving reports of widespread avalanche activity that occurred earlier this week across the region, for example as described in this MIN as well as this MIN. We also heard of a deep persistent slab releasing out of treeline terrain on a north aspect near Ningunsaw.
Looking towards Friday, natural avalanche activity may taper but skier and rider triggering is likely. Strong winds may build fresh and reactive wind slabs. A conservative mindset is warranted and avoid slopes with any negative consequence, as triggering storm and wind slabs will remain likely.
By Thursday afternoon the region received 20-30 cm of fresh snow. The new snow arrived with strong to extreme southwest to northwest wind. Reactive storm slabs likely exist in sheltered terrain and wind slabs in exposed terrain at high elevations.
This snow will build on the 40 to 60 cm of snow that accumulated earlier this week. All of this snow overlies hard wind-affected snow in exposed terrain and weak, faceted snow or surface hoar crystals in sheltered terrain, suggesting it may take some time for the snow to bond to these surfaces.
Basal faceted snow remains part of the snowpack structure in much of the region. Once we see a substantial warm-up, we'll be thinking about the potential for the reactivation of basal layers.
