It looks like the South Columbias will largely be out of the storm track until Thursday. With all the surface hoar around we will likely have a serious avalanche problem on our hands when it does start snowing again.
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A Pacific frontal system is generating rain and strong winds over the coastal regions today (Tuesday). This system will move into the South Columbia Tuesday night and should produce 5 to 10cm of snow above 500m. No new snow is expected Wednesday. On Thursday 2 to 15cm of snow are expected as the freezing level rises from the valley bottom to around 1600m in the afternoon. A third pulse Thursday night should deliver an additional 2 to 15cm as the freezing level hovers around 1500m. Gusty SW winds will likely blow through the forecast period. Its important to take snowfall amounts with a grain of salt with a pattern as dynamic as this one. For more detailed mountain weather information visit: avalanche.ca/weather
Avalanche Summary
Natural loose dry avalanches from size 1.5 to 2 were reported from alpine features facing North, Northeast, East and and Southeast over the weekend.
Snowpack Summary
Our relatively young snowpack is already quite complicated. Northerly winds associated with last weeks outbreak of Arctic air stripped many south facing features near ridgecrest. As a result, tired old wind slabs have been reported on north facing features at and above treeline. The cold air and associated inversion created trophy surface hoar that seems to average around 20mm in size and can be found from creek bottom up to around 1800m. Sun and above freezing alpine temperatures were also part of the last week, so you're likely to find a suncrust on solar aspects (south and west) at and above treeline. The three different November surface hoar interfaces that we were previously concerned about seem to be a thing of the past and are not producing any activity. Its thought that there is a crust/facet interface on or just above the ground on high elevation north facing features, but the lack of observations surrounding this interface make us think that this is a very isolated problem, and it has likely become inactive.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.