Avalanche forecast

Northwest Coastal

Feb 22 – 23, 2012Avalanche Canada
View on map
Archived · expired 15 years ago

Avalanche danger

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Moderate to strong winds combined with new snowfall will create new and reactive wind slabs on lee terrain. Expect wind slab development to occur throughout the forecast period.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    This new snow may create touchy storm slabs that sit on a variety of buried weak layers. The slab that sits on these layers is up to 40cm thick, and growing.

Confidence

Fair - Intensity of incoming weather is uncertain on Friday

Weather Forecast

Thursday: A ridge of high pressure brings isolated flurries with, cooler conditions. Alpine temperatures near -7. Ridgetop winds 30km/hr from the W. Friday: Snow amounts 10-20cms during the day. Ridgetop winds strong from the SW. Treeline temperatures near -7. Saturday: Mainly cloudy with light snow fall amounts, and light to moderate outflows. Freezing levels should remain at valley bottom through the forecast period.

Avalanche Summary

Reports across the region of widespread size 1-2 natural avalanche activity. Majority of aspects being NE-N. Many of these are reported as wind slabs releasing on buried crusts that formed mid February. In the Eastern area of the region a size 2.5 natural avalanche occurred on February 21st. This occurred on an East aspect @1700m, running 900m in length. Wind slab activity up to size 2 on Southerly aspects have also been reported. On February 20th a natural size 2.5-3 was reported from Mt. Rainy. With forecast wind and snow for Friday, I suspect avalanche activity to increase.

Snowpack Summary

Generally, up to 35 cm of new snow sits over a strong melt freeze crust that exists below 1000m on all aspects, and over wind-pressed powder on shaded alpine features. Facets and surface hoar have been found sandwiched between the newer snow and the old surfaces at treeline and below. This surface hoar seems to be more predominant in inland areas. Where it exists, this layer has started to become reactive under the new load and slab development. I suspect this will continue as the forecast snow and wind continues. If forecast sunny skies prevail Thursday afternoon, keep an eye on solar slopes, and watch for deterioration within the snowpack. The mid and lower snowpack is generally well settled and strong. Check out our Forecaster's Blog for some insight on incremental loading.

Regions covered