Avalanche Forecast

Issued: Jan 8th, 2017 4:02PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

jsmith, Avalanche Canada

Cariboos.

Wind is driving the avalanche danger on Monday. I would expect to find touchy wind slabs on lee features below ridgetops and good skiing in sheltered terrain.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

MONDAY: 10-20 cm of new snow is expected by Monday afternoon, moderate southwesterly ridgetop winds, and temperatures around -18. TUESDAY: Mostly sunny with cloudy periods, moderate northwesterly ridgetop winds, and temperatures around -20. WEDNESDAY: Mostly sunny with cloudy periods, moderate northerly ridgetop winds, and temperatures around -20.

Avalanche Summary

On Saturday, a size 1 skier triggered wind slab was reported on a southwest aspect. I expect human triggered wind slab activity to increase on Monday with the forecast new snow and wind.

Snowpack Summary

Forecast 10-20 cm of new snow by Monday afternoon and moderate southwest winds are expected to create fresh wind slabs on lee features at treeline and above. Recent snow has also covered old, thicker wind and hard slabs from previous wind events. Persistent and deep persistent weakness in the mid and lower snowpack are giving variable results in snowpack tests, but are generally most touchy in shallow snowpack areas. Recent snowpack tests gave moderate but resistant results on facets and/or surface hoar buried mid-December where it was found down 45 cm, and hard but sudden collapse results on the facet/crust weakness down 116 cm near the base of the snowpack.

Problems

Wind Slabs

Wind slabs could 'step-down' to deeper weak layers resulting in large, destructive avalanches. This is more likely in large, steep, and rocky alpine features with variable snowpack depths.

Watch for signs of weakness such as whumphing, cracking, and recent avalanches.Avoid areas where the snow feels stiff or slabby.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Triggering a weak layer of facets and/or surface hoar buried mid-December may still be possible in parts of the region where the snowpack is shallower. Dig down and test for weaknesses before committing to larger terrain features.

Only expose one person at a time to larger slopes.Avoid likely trigger spots such as steep and rocky areas with a shallow snowpack.Choose regroup spots that are out of avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 9th, 2017 2:00PM