Avalanche Forecast

Issued: Dec 11th, 2012 9:19AM

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

ccampbell, Avalanche Canada

South Coast.

Summary

Confidence

Fair - Due to limited field observations for the entire period

Weather Forecast

Wednesday: Partly cloudy with no significant precipitation expected, freezing levels in valley bottoms with treeline temperatures around -5 to -10 Celsius, and moderate northwesterly winds. Thursday: Increasing cloud throughout the day with light snow starting in the afternoon, freezing levels around 500-700m and moderate westerly winds becoming strong southwesterlies with the onset of precipitation. Friday: Snow easing throughout the day with 15-20cm total since Thursday, moderate westerly winds and freezing levels hovering around 500-700m.

Avalanche Summary

Recent reports include evidence of previous large avalanches from Mt Joffre at 2000m and the east face of Cayoosh Mtn in the Duffy Lake area (check out Wayne Flann's Avalanche Blog for a photo of the Cayoosh avalanche). Glide cracks are getting big and releasing to Size 2, and ski cutting has been producing heavy sluffs.

Snowpack Summary

A recent Rutschblock test at 2100m on a north aspect above Duffy Lake gave an RB3 whole block release down 30cm on a storm snow weakness. The late November surface hoar was found down 70cm but unreactive to snowpack testing. A well settled and rounding mid-pack is overlaying the early November crust, which gave a moderate 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 low density surface snow is causing a lot of sluffing in steeper terrain, but not reacting as a slab. 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

Expect to find very touchy wind slabs below ridge crests, behind terrain features and in cross-loaded gullies. Be especially diligent as northerly winds start to reverse load unusual aspects.

Avoid freshly wind loaded features.>Avoid travelling in areas that have been reverse loaded by winds.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Storm Slabs

Weaknesses within and under the recent storm snow (including surface hoar buried two weeks ago) are sensitive to human triggers. Low density storm snow is also sluffing readily.

On steep slopes, pull over periodically or cut into a new line to manage sluffing.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Valid until: Dec 12th, 2012 2:00PM