Northwest Coastal

Recent storm loading, buried weak layers, high freezing levels and solar radiation are a perfect recipe for widespread avalanche activity on Tuesday.

Moderate - Timing or intensity of solar radiation is uncertain on Tuesday

On Tuesday expect mainly clear skies, moderate southwest ridgetop winds and freezing levels around 3000m. On Wednesday and Thursday the region should see light snowfall (3-5cm each day), strong southwest winds and freezing levels at about 1700m.

On Saturday explosives control in the Stewart and Ningunsaw areas produced deep persistent and storm slab avalanches in the size 2.5-3 range. While most avalanches observed failed within recent storm layers, a few failed on basal facets in shallow snowpack parts of the region. There was also a recent size 3 natural persistent slab avalanche north of Stewart. This avalanche failed on the January 9th surface hoar.Closer to Terrace, a few recent storm slab avalanches to size 3 were observed between 1200 and 1700m. A skier also triggered a size 1.5 wind slab avalanche on a southwest aspect at 1450m. The skier was not injured.I'm sure there was a decent round of storm slab activity on Sunday and Monday in response to new snow and wind. Looking forward, solar radiation and skyrocketing freezing levels will spark a widespread round of loose wet avalanche activity. Warming will also promote cornice falls, wet slabs and persistent slab avalanches failing on deeper, more destructive weak layers.

On Sunday a warm, wet and windy storm added mass and reactivity to recently formed storm slabs. 24 hour snow totals were around 40cm in the Terrace area with closer to 70cm falling in the mountains around Stewart. Rain on Monday, and then rising freezing levels and solar radiation will likely leave most surfaces moist or wet on Tuesday. This warming will also have a significant destabilizing effect on the snowpack. The January 9th surface hoar/facet layer is down 70-200 cm and remains a concern, especially with heavy and/or thin-spot triggers. Around the same depth you may also find a surface hoar/facet interface from around New Years. There continues to be a lot of uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem; however, forecast warm temperatures and solar radiation will increase the likelihood of triggering these layers where they still exist. A very conservative approach to mountain travel is still required.