Avalanche Forecast
Issued: Mar 17th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
wlewis,
Avalanche Canada
Avoid steep open slopes capable of producing large avalanches. Storm snow is expected to remain reactive.
Keep decision making conservative and give the snowpack time to stabilize.
Summary
Confidence
Moderate
Avalanche Summary
We expect a natural avalanche cycle occurred over the day on Thursday during periods of rapid loading. Natural activity could continue into Friday with more snow followed by sunny conditions. Human triggering is very likely given the amount of new snow and what it is resting on.
Natural avalanche activity could continue during periods of intense sun or wind loading. Avoidance of avalanche terrain is recommended until the snowpack has time to adjust.
Snowpack Summary
Around 50 cm of storm snow has fallen around White Pass, with lesser amounts as you move east. Southerly winds have built deeper deposits north facing terrain features near ridges. Storm snow overlies previously wind affected snow (sastrugi) in exposed areas and faceted snow in sheltered features. The new snow may not bond well to these previous surfaces.
The storm snow is also loading a buried weak layer of surface hoar found about 80 cm deep in Powder Valley, Tutshi, and Paddy Peak areas and approximately 150 to 200 cm around White Pass. This layer is most prominent on northerly slopes sheltered from the wind. On other aspects, this layer is a hard melt-freeze crust with weak facets around it. To date this layer is has been most problematic in alpine terrain.
The remainder of the middle of the snowpack is consolidated and strong. Weak faceted grains are found near the base of the snowpack, particularly in thin snowpack areas.
Weather Summary
Friday Night
Cloudy, with strong southerly winds. Freezing levels drop to valley bottom. Up to 3 cm of snow overnight.
Saturday
Partly clear skies with moderate southeast winds. Freezing levels reach 800 m, alpine high temperatures of -7 °C.
Sunday
Cloudy with light southeast winds. Up to 5 cm of snow. Freezing levels reach 800 m.
Monday
Cloudy. Light snowfall continues with light and variable winds. Freezing levels around 500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Be aware of the potential for large, deep avalanches to run full path or even longer.
Problems
Storm Slabs
Up to 50 cm of storm snow with strong southerly winds has formed a widespread and reactive storm slab.
Expect deeper and more reactive deposits on north facing terrain features. Periods of strong sunshine on Saturday can quickly destabilize the snow on sun-affected slopes, increasing reactivity.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
The new snow is loading a weak layer of surface hoar and/or faceted grains around a hard crust, which increases the likelihood of triggering an avalanche on this layer. The layer is buried around 80 cm in the eastern portions of the region and up to 200 cm around White Pass. This layer has previously produced widely propagating avalanches in alpine terrain and it is capable of being remotely triggered from a distance. The most likely area for riders to trigger it is in wind-sheltered, north-facing terrain, and in rocky terrain where the snowpack is thin.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 18th, 2023 4:00PM
