Avalanche Forecast

Issued: Dec 17th, 2013 8:31AM

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

rbuhler, Avalanche Canada

South Rockies.

This forecast is based on very limited data. If you are out in the mountains, we would like to hear from you at forecaster@avalanche.ca

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

A ridge of high pressure will build late-Wednesday, bringing clear and cold conditions for Thursday. On Friday, the next frontal system should reach the region possibly resulting in light precipitation.Wednesday: Light snowfall, freezing levels dropping to valley bottom, light SW winds switching to NE as the ridge builds.Thursday: Clear conditions, freezing levels at valley bottom, light windsFriday: A mix of sun and cloud, light precipitation possible, light winds

Avalanche Summary

On Monday, reports of two wind slab avalanches size 2.5 triggered by explosives south of the Crowsnest Pass and one size 1 wind slab avalanche triggered by a vehicle in the North Flathead area.

Snowpack Summary

Recent incremental snowfall has started to bury the mid-Dec surface hoar and the previously faceted upper snowpack. Snowpack depths at treeline seem to vary from 50 - 110 cm with high variability in wind-exposed areas. Buried surface hoar/facets/crust (late-Nov interface) are down approximately 30-40cm. The base of the snowpack is made up of weak facets and depth hoar. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on a steep, convex slopes. In some below treeline areas the snowpack is below threshold and early season hazards like open creeks and stumps remain a concern.

Problems

Wind Slabs

Wind slabs have developed recently on a variety of aspects due to shifting winds. Expect to encounter these deep deposits of wind-transported snow below ridge crests and behind terrain features.

Be careful with wind loaded pockets. Be aware of wide variation in snowpack depth>Be cautious as you transition into wind affected terrain.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Persistent Slabs

Sugary facets at or near the base of the snowpack are most likely triggered on steep, convex slopes with a thin snowpack. In deeper snowpack areas you may find a stubborn buried surface hoar layer.

Avoid shallow snowpack areas on steep, convex terrain where triggering is more likely.>Dig down to find and test weak layers before committing to a line.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

1 - 4

Valid until: Dec 18th, 2013 2:00PM