Avalanche Forecast

Issued: Dec 14th, 2012 8:50AM

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

Avalanche Canada pmarshall, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Synopsis: A series of frontal systems bringing moderate to heavy snowfall and strong winds will affect the South Coast for the next few days.Saturday: Moderate snow – 10-15 cm. Winds increase to strong from the SW. The freezing level should remain near valley bottom. Sunday: A short break early in the day, then moderate to heavy snow overnight and into Monday (~10-15 cm). Winds increasing to strong from the SW with the arrival of the system. Freezing level near valley bottom. Monday: Heavy snow (primarily in southern areas). Freezing level could jump to 800 m.

Avalanche Summary

There were a few reports of small natural and human triggered loose snow avalanches on Wednesday and Thursday. Recent reports include evidence of previous large avalanches, including one from Mt Joffre at 2000m and the east face of Cayoosh Mountain in the Duffy Lake area last weekend (check out Wayne Flann's Avalanche Blog for a photo of the Cayoosh avalanche).

Snowpack Summary

Approximately 10 cm of new snow may have buried a thin layer of surface hoar in some areas. Moderate westerly winds have probably redistributed low density snow into soft wind slabs in exposed lee terrain. The late November surface hoar has been found down 70-90 cm but produces inconsistent results with snowpack testing. A well settled and rounding mid-pack is overlaying the early November crust, which continues to give occasional sudden planer compression test result in the overlying facets. Meanwhile in the Coquihalla area, recent reports suggest an overall well settled "right side up" (progressively more dense with depth) snowpack. The early November crust has not been found in the Coquihalla, although we don't have any reports from the high alpine. Conditions may be quite different in the Northern part of this region, please email us your observations if you are out in the field. forecaster@avalanche.ca

Problems

Wind Slabs

An icon showing Wind Slabs
Weak wind slabs may be encountered below ridge crests, behind terrain features and in cross-loaded gullies.
Avoid lee and cross-loaded terrain near ridge crests.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Watch for slopes that roll over such that the slab is unsupported from below. Particularly in areas with a shallower snowpack.
Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 15th, 2012 2:00PM