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Archived

Avalanche Forecast

Mar 8th, 2016–Mar 9th, 2016
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
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

The heaviest snowfall for the next few days is forecast for the extreme southwest corner of the region. Local avalanche danger could be higher in areas west of Terrace and south of highway 16. 

Confidence

Moderate

Weather Forecast

WEDNESDAY: Cloudy with light to moderate snow – 5-15 cm. The freezing level gradually climbs to 1200-1400 m near the end of the day. Ridge winds are light increasing to strong from the E-SE. THURSDAY: Periods of snow – 10-20 cm. The freezing level dips back to 800-1000 m by the end of the day and winds are moderate from the S-SE. FRIDAY: Cloudy with sunny breaks. The freezing level is around 1400 m and winds are light.

Avalanche Summary

Observations on Monday were limited due to poor visibility; however, there were a few reports of natural slab avalanches up to size 2 from immediate lee slopes in the alpine. There was also a report of a size 3 avalanche that initiated on a north aspect in the alpine, and a large natural cornice fall. Expect wind slabs to remain sensitive to rider triggering in steep exposed terrain.

Snowpack Summary

Over the past few days we've seen snowfall accumulations of 5-15 cm each day, and storm snow totals of around 40-60 cm. Strong to extreme ridgetop winds have shifted the new snow into hard or soft wind slabs at treeline and in the alpine, adding to an ongoing wind slab problem. Some areas are reporting a weak surface hoar layer near the base of the most recent storm snow. An old crust buried in early February can now be found around 80-120 cm below the surface. This crust, which may coexist with small facets or decomposing surface hoar, recently produced sudden planar ("pops") results in snowpack tests. Although no recent avalanches were reported to have failed at this interface, I'd remain suspicious of this layer in steep, unsupported terrain at treeline and in the alpine.

Avalanche Problems

Wind Slabs

This ongoing windy and stormy period has led to widespread hard and soft wind slab development in lee and cross-loaded terrain. The wind direction has been variable, meaning all aspects are suspect.
Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Storm Slabs

Weaknesses may exist within or at the base of the recent storm snow. In some areas up to 60 cm of fresh snow sits on a weak surface hoar layer. Look for this in sheltered terrain near treeline. 
Avoid steep slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

Cornices

Cornices are very large and could fail with continued growth and/or warming.
Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 4