Confidence
Fair - Timing or intensity of solar radiation is uncertain on Sunday
Weather Forecast
Synopsis: Initially, a ridge of high pressure will bring dry, sunny weather for Sunday with increasing cloud through Monday. On Tuesday afternoon, a Pacific frontal system will bring precipitation to the region.Sunday: Dry and mostly sunny. Freezing level going as high as 2300 m. Light northerly winds.Monday: Should stay dry with cloud cover increasing through the day. Freezing level dropping to around 1000 m. Generally light winds, but westerly gusts to 60km/h at ridgetop are possible.Tuesday: Up to 5 cm new snow starting late in the day. Freezing level around 1000 m. Moderate or strong southwesterly winds.
Avalanche Summary
Human triggered avalanches occurred in a few areas outside, but immediately adjacent to this region. The avalanches were triggered on a variety of aspects, but a common theme appears to be the presence of a crust buried 30-40 cm below the surface. Loose wet avalanches were reported in response to solar warming.
Snowpack Summary
Around 30-40cm new snow fell on average during recent storms, which ended on Friday. The Coquihalla area received a little more (up to 65 cm). Consistent southwesterly winds during the storm period redistributed the new snow into windslabs and grew cornices on lee terrain features in the alpine and at treeline. The recently buried surfaces (Feb 3rd interface) are old wind slabs (behind ridges, ribs and on lee slopes) and sun crusts (on south and west facing slopes). In isolated locations, this interface comprises small surface hoar crystals. Down a further 20-50 cm sits a persistent interface comprising of crusts, facets and surface hoar crystals. This layer is now mostly unreactive, with only one size 2 avalanche reported (on Feb 6th) since the end of January. If it were to be triggered again, the most likely spot would be a steep convex roll on a sheltered north aspect slope around treeline. A recent Rutchblock test gave a score of 6 with a partial block release in the Duffey Lake area. The mid and lower snowpack pack layers are generally well settled.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.