Avalanche Forecast

Issued: Mar 14th, 2014 8:06AM

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

Avalanche Canada ccampbell, Avalanche Canada

For more insight into the current tricky conditions, see the latest Forecasters Blog.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Saturday: Mainly cloudy with scattered flurries bringing 5-10 cm depending on drainage. Mostly light westerly winds with strong gusts associated with snow flurry activity. Freezing levels as high as 2000 m in the far south, but 1500 m in the north. Sunday: Cloudy with flurries bringing 10-20 cm depending on drainage. Generally moderate but gusty westerly winds. Freezing levels dropping slightly to 1800 m in the south and hovering at 1500 m in the north. Monday: A mix of sun and cloud with isolated flurries, but I would'nt be surprised if some drainages got another 10-20 cm. Generally light westerly winds gusting with flurry activity, and freezing levels down to 1400 m.

Avalanche Summary

Expect fresh wind slab and loose dry snow avalanche activity to increase throughout the forecast period as snow flurries load exposed alpine and treeline feature. At treeline elevations and below, significant warming has made large persistent slab avalanches are highly sensitive to human triggers. In parts of the forecast area, very large destructive avalanches running to valley bottoms from major start zones remain a  concern. Neighboring forecast regions have recently reported large avalanches initiating in the new storm snow, then stepping down to deeper layers, some running full path to the ground. Cornice failures triggering large deep persistent avalanches have also been reported.

Snowpack Summary

A 50-70 cm slab is bonding poorly to buried surface hoar and facets particularly on sheltered slopes such as cut blocks, and crust on previously sun-exposed slopes.  Warm temperatures and sun-exposure has been making these and deeper persistent slabs very sensitive to triggers at treeline elevations and below, and resulting in surface melt-freeze cycles as high as alpine elevations. The deeper facet/crust persistent weakness buried at the beginning of February, now down 60 to 160cm, has been described by avalanche professionals as "very weird". Although widespread, it has been highly variable in terms of reactivity. Convective flurry activity has already accumulated 10-15cm of fresh snow in some drainages, which has likely blown into touchy wind slabs on leeward slopes. Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.

Problems

Storm Slabs

An icon showing Storm Slabs
Dynamic conditions are changing with elevation and throughout the day, due to  warming, sun-exposure, snow flurries, and wind. Old storm (persistent) slabs lurk on sheltered low-elevation slopes, while fresh slabs may form on exposed lee slopes.
Choose conservative lines and watch for clues of instability.>Be alert to conditions that change with elevation.>Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Due to the high variability and significant potential consequences associated with a deeply buried facet/crust weakness, avalanche professionals have been maintaining a high level of caution and discipline.
Be aware of the potential for large, deep avalanches.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 15th, 2014 2:00PM