Avalanche forecast

Northwest Inland

Dec 20 – 21, 2011Avalanche Canada
View on map
Archived · expired 15 years ago

Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Wind slabs have developed on lee and cross-loaded terrain in the alpine and at treeline. Rider triggered wind slabs are likely; especially on the mid December surface hoar/facet/crust interface.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Reactive storm slabs have now formed at all elevations. Especially where the mid December buried surface hoar/crust/facet interface is lurking.

Confidence

Fair - Intensity of incoming weather is uncertain on Thursday

Weather Forecast

Wednesday: Mainly dry, cloudy conditions. Treeline temperatures near -7. Ridgetop winds Light from the southwest in the am, becoming strong in the pm. Thursday-Friday: Snow amounts each day up to 5cm. Ridgetop winds strong from the southwest. Freezing levels may rise to 1000m then falling back to valley bottom.

Avalanche Summary

On saturday evidence of a size 2 natural avalanche cycle was reported in the Hankin area. There was also human triggering to size 2.5 in the same area. It is thought that these slides are releasing on the crust/surface hoar/facet interface. Any information (professional or recreational) from the field is highly appreciated. Please send your observations to [email protected].

Snowpack Summary

Monday -Tuesday the region received up to 20cms of new snow accompanied by strong southwest winds. Storm snow and wind slabs are forming. There could be up to 50cms total from last week's snowfall and the current snowfall loading the weak layers in the upper part of the snowpack. These weak layers are the December 12th surface hoar/crust/facet combo. What is the tipping point of this weak interface? In areas where this interface has reached its threshold avalanches have occurred. If they have yet to happen naturally, I suspect they are very touchy and will react to a rider trigger. Observations suggest there is faceting above and below the crust. The crust being a result from rain in the early December dry spell. This crust is widespread and is lingering in most start zones up to 2000m. In short, the upper snowpack is variable and showing easy shears in test results. The midpack seems to be well settled and strong.

Regions covered