Avalanche Forecast
Issued: Mar 21st, 2015 8:02AM
The alpine rating is Persistent Slabs and Storm Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeThe current snowpack structure is atypical for this region, especially at this time of year. Check out this blog post for more details: http://www.avalanche.ca/blogs/VQxmdCUAAJZDmnXn/rainsnowwind
Summary
Confidence
Fair - Due to the number of field observations
Weather Forecast
A ridge of high pressure will form on Sunday delivering a mix of sun and cloud. By Sunday afternoon, an unstable air mass will bring intermittent convective snowfall which should result in light to locally moderate accumulations for the rest of the forecast period. Ridgetop winds should remain generally moderate from the southwest with daytime freezing levels hovering around 1500m.
Avalanche Summary
Over the past week, isolated slab avalanches to size 2 have occurred on persistent weaknesses buried on March 11th. In a few cases, avalanches failed with light inputs such as remote triggers from distances of up to 100m away. New snow and wind has created its own mix of reactive surface instabilities, but it has also added load to these deeper, more destructive layers. There's a fair bit of uncertainty as to how the March 11th interface will react to storm loading. That said, I'd resist heading into aggressive higher elevation as any avalanches on this layer would likely be destructive in nature.
Snowpack Summary
New storm slabs have formed in response to steady wind, snowfall and warm temperatures prior to the weekend. At lower elevations, rain has saturated the snowpack. Cornices may also be fragile. A touchy crust/facet persistent weak layer, buried up to 70 cm down, has started to play up in isolated terrain, especially in the north of the region (see avalanche summary). Avalanche problems associated with this layer may linger for a while with the potential for surprisingly large and destructive avalanches. Below this, the snowpack is reported to be generally well-settled and strong.
Problems
Persistent Slabs
In the past week, people have remotely triggered large persistent slab avalanches. The spotty nature of this interface makes it difficult to manage. New snow has now overloaded this weak layer with the potential for surprisingly large avalanches.
Remote triggering is a concern, watch out for adjacent slopes.>Avoid steep convexities or areas with a thin or variable snowpack.>Pay attention to overhead hazards.>Choose conservative lines and watch for clues of instability.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
The recent storm has created dense slabs which should gain strength fairly quickly. That said, I'd remain cautious of triggering large avalanches in higher elevation lee terrain. Cornices formed by the storm may also be large and weak.
Be alert to conditions that change with elevation.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 22nd, 2015 2:00PM