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RegisterDec 15th, 2020–Dec 16th, 2020
South Coast Inland.
Periods of heavy snowfall in the Coquihalla Pass area with strong SW winds will create dangerous avalanche conditions. Choose conservative terrain & avoid overhead hazard. Lower danger of CML rating in the Duffy or where total new snowfall amounts are less than 30cm.
A series of fast moving storms moves through the region with scattered snow flurries and moderate to strong winds. The Coquihalla region is forecast to receive heavier snowfall amounts of 20-30cm overnight Tuesday with more snow on Wednesday.
Tuesday night: Mainly cloudy with isolated flurries with trace-5cm (Duffy) and up to 20cm (Coquihallla), strong southwest ridgetop wind gusting strong, alpine low -7 C, freezing level 1000 m.
Wednesday: Cloudy with scattered flurries, trace (Duffy) to 15cm new snow (Coquihalla), light to moderate south ridgetop wind, alpine high -4 C, freezing level 1300 m. Heavier snowfall amounts shifting inland and east.
Thursday: Cloudy with snow flurries, 5-15 cm new snow, light to moderate westerly wind, alpine high -1 C & alpine low -6C, freezing level 1200 m.
Friday: Flurries with new snow amounts of 5-10cm (Duffy) and 20-25cm (Coquihalla), wind increasing to moderate southwest gusting strong, freezing level 1200 m.
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.