Avalanche Forecast

Issued: Dec 15th, 2013 8:24AM

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.

Summary

Weather Forecast

Strong west to northwesterly zonal flow continues for the southern interior on Monday and Tuesday. On Tuesday, a low pressure system will move onto the central coast. The system will likely track to the north of the region on Wednesday but light precipitation and the breakdown of the warm air is expected.Monday: A mix of sun and cloud, freezing levels around 2000m, moderate westerly alpine windsTuesday: A mix of sun and cloud, freezing levels as high as 2300m, moderate westerly alpine windsWednesday: Mostly cloudy, light precipitation, freezing levels dropping to valley bottom, alpine winds decreasing

Avalanche Summary

No natural avalanche activity reported since Thursday. On Saturday, some human-triggered activity was reported in the Fernie area (see Lizard Range forecast).

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. Recent snowpack testing on this persistent weakness gave easy results and some whumpfing. 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

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 - Possible

Expected Size

1 - 4

Valid until: Dec 16th, 2013 2:00PM