Avalanche Forecast
Issued: Dec 20th, 2014 8:02AM
The alpine rating is Storm Slabs and Deep Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeForecast new snow and wind are expected to result in Considerable avalanche danger. If you see more snow than forecast in your area, then consider these danger ratings to be a bit low.
Summary
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Strong to very strong Southwest winds overnight combined with 10-15 cm of new snow and freezing levels rising up to 1300 metres. Snow ending Sunday morning with a chance of flurries during the day combined with strong Westerly winds and freezing levels rising up to about 1600 metres. Drier and cooler on Monday as a weak ridge of high pressure builds over the region. The next pulse of moisture is forecast to move in from the coast sometime on Tuesday. Models are not in agreement with regard to timing, location, or intensity.
Avalanche Summary
No new reports of avalanches. Expect new storm slab avalanches to increase as the new storm develops.
Snowpack Summary
The new storm is expected to develop a storm slab above the mix of old surface forms that include hard crusts, near surface facets, and surface hoar. In the Coquihalla there is 65-80 cm of snow on the ground above 1600 metres elevation, and below threshold for avalanches below 1500 metres. The recent surface hoar has been reported to have been mostly blown away by the Northeast wind before this new storm. In the North of the region it sounds like the recent surface hoar is 2-4 mm at treeline and up to 30 mm near open creeks below treeline. The knife hard December melt-freeze crust extends up to about 2100 metres and then tapers off to nothing by 2300 metres. The new storm slab may be up to 40 cm in the North of the region, and it may not be bonding well to the old crust/ surface hoar combination. The November crust is deeply buried and may become easier to trigger in isolated areas if the load from the storm slab overcomes the bond at the crust interface.
Problems
Storm Slabs
Storm slabs are expected to continue to develop with forecast wind and new snow. Wind transported snow may be deep and not bonding well to the old surface.
Give cornices a wide berth when travelling on or below ridges.>Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.>Avoid freshly wind loaded features.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The increasing load of new storm snow may increase the likelihood of triggering the deeply buried weak crust layer.
Avoid convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 21st, 2014 2:00PM