Avalanche Forecast

Issued: Mar 8th, 2016 7:39AM

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

Avalanche Canada pmarshall, Avalanche Canada

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. 

Summary

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.

Problems

Wind Slabs

An icon showing 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

An icon showing 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

An icon showing 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

Valid until: Mar 9th, 2016 2:00PM

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