Avalanche Forecast
Issued: Jan 20th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
shorton,
Avalanche Canada
Triggering avalanches remains possible with wind slabs at upper elevations and deep persistent slabs in steep rocky terrain.
Summary
Confidence
Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.
Weather Forecast
WEDNESDAY NIGHT: Clear skies, light northeast wind, treeline temperatures around -8 C.
THURSDAY: Mostly sunny, light northeast wind, treeline temperatures around -6 C.
FRIDAY: Sunny, light north wind, treeline temperatures around -5 C.
SATURDAY: Increasing cloud during the day, moderate northwest wind, treeline temperatures around -10 C.
Avalanche Summary
Extreme wind on Tuesday resulted in a natural cycle of wind slab avalanches, with rain causing some wet loose avalanches below 1000 m. Natural wind slab avalanches to size 2 were observed over the weekend, and skiers easily cut size 1 slabs on loaded slopes.
Deep persistent slab avalanche activity has been more sporadic (as it often is). A size 2.5 deep persistent slab avalanche was reported from Skilokis over the weekend, that appeared to be triggered by a cornice and failed on a facet/crust layer. Explosives triggered a few size 2.5 persistent slab avalanches near the southern boundary of the region on Jan 7 as well as some very large size 3-4 deep persistent slab avalanches at Ningunsaw in the far north of the region over the past few days. These are reminders of this low-probability / high-consequence scenario.
Snowpack Summary
Another 5-20 cm of snow on Tuesday added to the recent incremental snowfalls. Gusty and variable winds have impacted loose snow and developed slabs in exposed areas. Warm temperatures have produced a crust up to 1000 m and higher on solar aspects. A few isolated surface hoar layers were observed forming over the past weeks and would now be 30-60 cm deep if preserved, but these layers have not been reported in recent snowpack and avalanche observations. The main snowpack feature we are tracking is two crusts in the lower snowpack that have some weak faceted snow around them. Reports from the Smithers area suggest the upper crust is 70-140 cm below the surface and has shown signs of being possible to trigger from shallow areas. The deeper crust is near the bottom of the snowpack and is most likely to trigger from steep rocky slopes (especially in thinner areas like the Babines).
Terrain and Travel
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Conditions may have improved, but be mindful that deep instabilities are still present.
- Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
Problems
Wind Slabs
On Tuesday strong west wind and a moderate amount of new snow formed widespread wind slabs at higher elevations. They should become less reactive in the coming days, but are still possible to trigger on steep alpine slopes and along ridgetops.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
In shallow snowpack areas weak faceted snow can be found around crusts roughly 100 cm below the surface. Human triggering a slab above this weak layer is possible on isolated shallow rocky slopes. The most recent avalanches on these layers have been reported east of the Bulkey Valley and at Ningunsaw.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 21st, 2021 4:00PM
