Avalanche Forecast

Issued: Dec 1st, 2015 8:43AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Wind Slabs.

Avalanche Canada ghelgeson, Avalanche Canada

It looks like the Purcells will largely be out of the storm track until Thursday night. With all the surface hoar around we will likely have a serious avalanche problem on our hands when it does start snowing again.

Summary

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 Purcells Tuesday night and should produce a trace of snow above 500m. No new snow is expected Wednesday. On Thursday 1 to 5cm of snow are expected as the freezing level rises from the valley bottom to around 1500m in the afternoon. A third pulse Thursday night should deliver an additional 2 to 10cm 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

The only recent avalanche activity reported has been loose snow sluffing from steep north facing terrain.

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

An icon showing Wind Slabs
Previously strong north winds formed wind slabs that extend from treeline to just below ridge crest. Most of these wind slabs are probably old, tired and hard to trigger, but there may be a few that remain sensitive to human triggering.
It's best practice to use ridges or ribs to avoid pockets of wind loaded snow at this time.>Be cautious as you transition out of wind sheltered terrain and avoid features that are actively being wind loaded.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 2nd, 2015 2:00PM