Newly formed storm slabs are expected to be touchy on Tuesday, especially in wind loaded terrain. Persistent slab avalanches remain a concern and very large avalanches are still possible. Conservative terrain selection remains critical.
A persistent slab problem formed by a crust down 60-130 cm has created a low likelihood, high consequence scenario that is difficult to forecast. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack.
Storm slabs are expected to remain very reactive to human triggering on Tuesday, especially in wind loaded terrain. These slabs overlie a weak interface and may remain touchy for an extended period.
Unsettled conditions are expected on Tuesday in the wake of the storm. Periods of light snow and sunny breaks are both possible.
Monday night: Snowfall 5-15 cm, moderate to strong SW wind, treeline temperature around -10 °C.
Tuesday: A chance of sunny breaks in the morning, light snow in the afternoon 2-4 cm, light to moderate SW wind, treeline high around -14 °C.
Wednesday: A mix of sun and cloud with a chance of flurries in the morning, light to moderate N wind, treeline high around -20 °C.
Thursday: Periods of light snowfall 2-4 cm, moderate to strong SW wind, treeline high around -16 °C.
Early reports from Monday include explosive triggered wind slabs up to size 2 and a ski cut produced a size 1 storm slab. No new avalanches were reported on Sunday. On Saturday, explosives triggered a size 1.5 wind slab. On Friday, explosives triggered a size 2.5 wind slab avalanche that stepped down to the persistent slab layer on a SE aspect near treeline.
While recent reports of large persistent slab avalanches have been minimal in the region, neighbouring regions including the Lizard-Flathead have seen some concerning avalanches recently including this one on Sunday.
On Tuesday, recently formed storm slabs and wind slabs are expected to remain reactive to human triggering. These new slabs sit on a weak interface and may be very reactive, especially in wind loaded terrain. The persistent slab problem remains a serious concern and the weight of the new snow may increase the reactivity of these deeper layers. Smaller storm and wind slab avalanches also have the potential to step down to deeper layers resulting in very large avalanches.
The new storm snow buried a highly wind affected snow surface and widespread facets from the recent cold conditions which is expected to create a weak bond with the new snow. The new snowfall may have been accompanied by moderate to strong winds and new storm slabs are expected to be most reactive in wind loaded areas.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 60-130 cm. In the past week, we have seen explosive triggered activity on this layer as well as snowpack tests that have shown that the layer remains reactive. Neighbouring regions have seen very large avalanches on this layer over the past week. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
