Bulletin d’avalanche

Lizard-Flathead

Feb 10, 2018Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Choose simple terrain while avoiding all overhead hazard this weekend: The snowpack has several buried weak layers. Special Avalanche Warning in effect for the interior ranges. Copy this address to view details: http://bit.ly/2nSOUyX

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2.5
    New snow and strong wind have formed reactive storm slabs particularly in wind exposed areas above 1700 m for the Fernie area, while eastern areas saw deeper snow accumulations at lower elevations as well.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–4
    Large avalanches have been running on deep weak layers. Wind loading, fragile cornices, and smaller avalanches are all possible triggers, as well as thin or rocky snowpack areas where human triggering may also be possible.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We're looking at a break from the stormy weather pattern and cool temperatures for the foreseeable future. Overnight lows will be near -20 Celsius at tree line. SATURDAY: Mostly sunny. Ridge wind light, west. Temperature -9. Freezing level valley bottom.SUNDAY: Mostly sunny with possible isolated flurries. Ridge wind light, east. Temperature -9. Freezing level valley bottom.MONDAY: Mix of sun and cloud. Ridge wind light, northeast. Temperature -12. Freezing level valley bottom.

Avalanche Summary

Thursday, explosive control produced storm slab results up to size 2 between 1700-2100 m. And on Wednesday ski cuts produced only small results up to size 1 in pockets of wind slab up to 20 cm deep.On Tuesday a snow cat remotely (from a distance) triggered a size 3-3.5 persistent slab avalanche that stepped down from 80-250 cm and ran to ground in the lower start zone on a south aspect at 2100 m. Explosive control work also produced cornice releases up to size 2.5, but failed to produce any slab results on the slopes below. Last weekend, the east facing Mt. Corrigan slidepath produced a very large, natural avalanche. The avalanche is estimated to be a size 4.0, and it took out mature timber in the path as it overran the Flathead FSR south of Corbin.

Snowpack Summary

Wednesday night's warm temperatures and fluctuating freezing levels brought light cover of new snow (5 cm) and 15 mm of rain up to 1700 m, with deeper snow accumulations at higher elevations. A temperature drop during the day on Thursday has formed a new surface crust up to 1700 m, and winds have redistributed the new snow (5-14 cm into Friday) at higher elevations.Below the snow surface two more crusts that formed late January and early February and are now buried 20-40 cm below 1700 m in the Fernie area. For the past month there has been regular avalanche activity on multiple weak layers in the mid and lower snowpack. A layer buried mid-January is composed of surface hoar on sheltered aspects (especially prominent from 1400-1900 m) and a sun crust on solar aspects and is 60-80 cm deep. Another surface hoar layer from early-January is 90-110 cm deep. A widespread weak layer from mid-December composed of facets, crusts, and surface hoar is 120-160 cm deep. Finally, a rain crust with sugary facets buried in late-November is near the base of the snowpack.

Régions couvertes