Avalanche Forecast

Issued: Jan 27th, 2012 11:20AM

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

pgoddard, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Timing of incoming weather is uncertain on Saturday

Weather Forecast

Saturday: Very heavy precipitation, starting early morning as a warm front arrives. Mild temperatures. Freezing level rising through the day to around 1200m. Strong to gale southerly winds at ridge top. Sunday: Moderate snow continues. Freezing level staying near 1200m. Strong westerly winds.Monday: A break from heavy snow, although a weak disturbance may bring light snow in the afternoon. Freezing level falling back to valley floor.

Avalanche Summary

A natural avalanche cycle to size 3 (most at size 2) occurred on Wednesday and Thursday. Skiers triggered numerous size 1 slabs on Thursday, failing on an instability in the storm snow.

Snowpack Summary

Heavy new snow has arrived this week and looks set to continue through the weekend. Roaring winds from the north-west, west and south-west have created new wind slabs at all elevations. Older, buried wind slabs were formed from northerly winds and are of particular concern at treeline and below. Dynamic weather will continue to affect the region through the weekend, which is likely to cause further wind slab and storm slab development. Of concern in the snowpack is a buried facet layer (down about 80-120cm) which is getting an ever-increasing load above it. It is beginning to produce destructive avalanches in some areas as a critical balance is reached. Below treeline, a crust /facet combo buried in early January is producing easy, sudden collapse results in compression tests.

Problems

Wind Slabs

Wind slabs may be found on many slopes due to strong, shifting winds and large amounts of snow available for transport. These overlie weak layers in the upper snowpack and can fail as very large, destructive avalanches.

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

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

2 - 7

Storm Slabs

Weaknesses exist within and below the deep storm snow. These have been producing avalanches all week. Very heavy new snow, combined with warming temperatures and wind this weekend should lead to a widespread avalanche cycle.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 7

Valid until: Jan 28th, 2012 8:00AM