Avalanche Forecast

Issued: Dec 4th, 2011 8:54AM

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

ghelgeson, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

A radical above freezing layer is forecasted for Sunday night into Monday. Freezing levels as high as 2800m are possible. A cold front sweeps across the NW coast bringing as much as 30mm to the region Monday afternoon as ridgetop winds build to 80 - 95 km/h out of the W. Freezing levels lower Monday as the cold front moves inland.Cold post frontal air keeps the region dry & cool on Tuesday. Ridge of high pressure rebuilds Wednesday & Thursday with an outflow pattern. Another above freezing layer is forecasted for later in the week.

Avalanche Summary

Control work produced avalanches up to size 4.0 in the northern reaches of the forecast region. There are no reports of human triggered avalanches from the region.

Snowpack Summary

Very strong SW-NW winds may wreak havoc on the snowpack creating scoured areas and soft or hard wind slabs in exposed lee terrain and cross-loaded gullies or terrain features. Coastal areas are reporting a very deep and strong snowpack which is at or near record levels for this time of year. A buried surface hoar layer may be found down 100-150cm near Terrace, but there is no recent information on the presence and sensitivity of this layer.

Problems

Wind Slabs

Big westerly winds combined with new snow will create fresh sensitive windslabs on lee aspects. These new windslabs will be burying old hard windslabs that may still be sensitive to human triggers.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Storm Slabs

Storm slabs will be an increasing problem throughout the day Monday. Carefully re-evaluate each run to account for changing conditions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Dec 5th, 2011 8:00AM