Avalanche Forecast
Issued: Dec 10th, 2016 3:47PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
rbuhler,
Avalanche Canada
Wind slabs should be expected in exposed terrain throughout the region on all aspects due to recently shifting winds. A weakness below the recent storm snow may increase the reactivity of these wind slabs.
Summary
Confidence
Moderate - Due to the number of field observations on Saturday
Weather Forecast
Light snowfall is expected to continue Saturday overnight and into Sunday. Weather models are currently showing another 5-15cm of snowfall by the end of the storm. On Sunday, freezing levels are expected to be at around 500m and alpine winds are forecast to be moderate from the southwest switching to northwest in the afternoon. On Monday, dry conditions are expected with a mix of sun and cloud. Treeline temperatures are expected to be below -10C and alpine winds should be light from the north. Sunny, dry, and cold conditions are currently expected for Tuesday.
Avalanche Summary
On Friday, one natural size 1 wind slab was reported. Ski cutting was also producing size 1 wind slabs in isolated terrain features that were loaded by recent strong northeast winds. A MIN post from Friday shows a 30cm thick wind slab which was triggered by a skier at treeline. On Thursday afternoon, strong winds resulted in a natural cycle of size 1-2 avalanches in steep wind-loaded alpine features. On Sunday, recently formed wind slabs are expected to be most reactive on north through east aspects from recent southwest winds. However, strong outflow winds on Thursday and Friday formed wind slabs on south and west aspects, and so wind slabs should be expected on all aspects in wind exposed terrain.
Snowpack Summary
High elevations were blasted with strong northeast outflow winds at the end of last week and are now experiencing moderate south winds and light snowfall. The result is extensive wind scouring and wind slab formation in exposed terrain. The new snowfall sits over a variable surface consisting of wind slabs, small isolated pockets of surface hoar, and surface facets. Expect the new snow to bond poorly with this interface. The mid-pack is generally strong, with a widespread mid-November crust buried 70-100 cm at treeline and anywhere from 30-200 cm in alpine terrain. Recent snowpack and explosive tests have shown the crust to be unreactive, but it could remain a problem in shallow alpine start zones.
Problems
Wind Slabs
Winds slabs may be lingering on all aspects due to recent winds from a variety of directions. These wind slabs may be sitting over a weak layer which is increasing the reactivity of these slabs.
Avoid freshly wind loaded features.Use ridges or ribs to avoid pockets of wind loaded snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 11th, 2016 2:00PM
