Avalanche danger will rise in response to another incoming storm. Danger ratings are based on expectations of a moderate storm. If local new snow amounts exceed 30 cm, increase the danger to HIGH.
New snow and wind will set up reactive storm and wind slabs on steep slopes during stormy conditions. Heavy snow areas such as the Coquihalla will be most likely to see avalanche activity.
Wednesday night: Snow with around 20cm for the Coquihalla and closer to 10cm elsewhere. Light southwesterly winds gusting strong, freezing level 1000m, alpine low 0C.
Thursday: Mainly Cloudy with isolated snow flurries, 5-10 cm new snow, light to moderate westerly wind, alpine high -1 C, freezing level 1100 m.
Friday: Heavy snow with around 30cm expected for the Coquihalla and around 15 cm elsewhere, wind increasing to moderate southwesterly gusting strong, alpine high 0C, alpine low -3C, freezing level 1200 m.
Saturday: Heavy precipitation with a mix of snow and rain, up to 50 cm/mm expected. Strong southwesterly ridgetop wind, alpine high +3C, alpine low -1C, freezing level expected to rise as high as 2000m.
Forecast heavy snow (20-30cm) and strong southwesterly winds will be creating heightened avalanche conditions overnight and into Wednesday in the Coquihalla Pass area.
On Sunday and Monday, MIN reports described skier triggered wind slabs size 1-1.5, 20-30 cm deep on steep, north facing slopes in both the Duffey (controlled) and Coquihalla (accidental skier triggered). This MIN From Nak & Thar on Monday reported ski cutting wind slab avalanches 15-20cm deep near ridgetop in immediate lee features. Thank you for the submissions, good to hear everyone is okay.
Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far!
By Wednesday morning, 20-40cm new snow is forecast to fall in the southern Coquihalla Pass region with strong southwest winds. Farther north near the Duffy, 10-25 cm of new snow is forecast. Strong southwesterly winds will form reactive windslabs in the alpine, at ridgecrest and in lee features. This new snow falls on a variety of surfaces: faceting soft snow, a thicker rain crust at treeline and below, a thin melt-freeze crust on solar aspects in the alpine, and possibly small surface hoar crystals in wind sheltered areas.
New snow has not been bonding well to the rain crust, which now sits between 20-40 cm deep in the alpine, depth tapering with elevation. In the south of the region, this crust is 10-20 cm thick and supportive. In the north, it exists as a thin "zipper" crust over 2300 m and may be punchy and unsupportive between 1600 and 2000 m.
In the north of the region, a crust/facet layer sits near the ground. The most recent avalanche activity observed on this layer was on December 1st when a natural cornice fall triggered a size 3. More recent snowpack tests in the Cayoosh zone found this layer down 100+ cm and unreactive. While our uncertainty around the reactivity of this crust is keeping it on the radar going into the active weather pattern over the next week or so, it does not appear to be an active problem at this time.
