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Avalanche Forecast

Mar 18th, 2012–Mar 19th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Monday: A mix of sun and cloud with a slight chance of flurries in some areas. The freezing level should be at valley bottom overnight, rising to 500-600m during the day. Winds are light, rising to moderate from the SE in the afternoon. Tuesday and Wednesday: Light to moderate snow - 10-15cm each day. The freezing level is around 500m and winds are moderate to strong from the S-SW.

Avalanche Summary

Some areas saw a fairly widespread cycle on southerly aspects on Friday and Saturday with avalanches up to Size 3. Other reports indicate primarily moist loose snow avalanches up to Size 2 on steep south aspects on Saturday. There are also reports of natural avalanches up to Size 3 on northerly aspects in the Bear Pass area.

Snowpack Summary

Sporadic strong and variable winds have redistributed moderate amounts of recent storm snow into wind slabs that most commonly exist in the lee of terrain features at treeline and in the alpine. The mid-pack varies greatly depending on location. You may find up to three persistent weak layers. First, a surface hoar layer buried mid-March, now buried 60-80cm deep, which seems to be most prevalent in the mountains around Stewart. Second, a surface hoar layer buried early March, buried around 1m deep, has been causing problems north of Terrace. Third, a weak layer comprising surface hoar or facets, buried early in February, is now more than 1m down. This has been causing issues particularly in the north around Ninginsaw. However, recent reports indicate this layer is becoming difficult to trigger. Bear in mind that triggering any of these persistent weak layers would likely result in a very large avalanche. Cornices in the region are reported to be very large and potentially unstable.

Avalanche Problems

Wind Slabs

Winds at ridgetop have been strong enough to blow snow into wind slabs behind ridges and other terrain breaks in the alpine and at treeline.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Loose Wet

Expect loose wet snow avalanches on steep solar aspects during the day if the sun is shining.

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Cornices

Cornices are reported to be very large and potentially unstable at this time, especially given the sunshine and warm daytime temperatures. A cornice fall could be destructive by itself, and may also act as a trigger on the slope below.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 6