Avalanche forecast

Purcells

Dec 7 – 8, 2012Avalanche Canada
View on map
Archived · expired 14 years ago

Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map

Highlights

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Strong winds and snowfall earlier in the week have been responsible for widespread windslab development. Although they have most likely gained considerable strength, triggering may still be possible in unsupported terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Two buried spotty surface hoar layers exist up to a metre down and seem to be most reactive in deeper snowpack areas. Where it they exist slopes may be ripe for human triggering, especially on unsupported terrain.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–6
    Recent heavy loading in some areas means that deep persistent slabs may only now be primed for triggering. Deep and destructive slides have been reported on this layer in a neighboring region.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight and Saturday: Light to locally moderate snowfall on Friday night with clearing on Saturday / moderate west winds becoming light and northwest with clearing / Freezing level at surfaceSunday: Light snowfall / Light northwest winds / Freezing level at surfaceMonday: Light snowfall / moderate west winds / Freezing level at surface

Avalanche Summary

Observations in the region have been limited; however, on Thursday explosives control produced avalanches to size 1.5 that ran within recent storm layers. There was also an isolated size 1.5 release that failed to ground in steep, unskiable, rocky terrain with crown depths to 85cm.Close to Invermere, a natural cornice release triggered a size 2 avalanche on a northwest facing alpine slope. The avalanche was about 120cm deep and ran on the early November faceted crust.

Snowpack Summary

In the upper snowpack light amounts of low density snow override wind slabs which were formed earlier in the week. In some areas, recent winds have also shaped unseasonably large cornices.Up to 75cm of  snow that fell over the past week may sit above a surface hoar layer that was buried at the end of November. Although not widespread in the region, releases on this layer may be likely if you have it in your area. Another surface hoar layer that developed during mid-november may exist up to 100cm down, and is still on the radar of professionals on the east side of the region.Near the ground is the early November crust. There are some facets below it, or it may appear as a sandwich of crusts and facets. In some areas it may only now be primed for triggering with recent heavy loading. Observations have been limited; however, deep and destructive slides have been reported on this layer in a neighboring region.In general, significant variations in snowpack structure exist across the region. Digging down and making your own observations will be critical to safe slope selection.

Regions covered