Bollettino valanghe

Northwest Coastal

Feb 3 – 4, 2013Avalanche Canada
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Archiviato · scaduto 14 years ago

Pericolo valanghe

Tue
Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte

In sintesi

There is dramatic variability across the region, and this forecast represents the areas hardest hit by the recent storms.

Problemi valanghivi

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–6
    The recent weather was prime for cornice growth.
  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–5
    Up to 80 cm sits above a persistent weakness comprising of a facet/surface hoar interface above 1000m and a crust below 1000m. The rain soaked surface snow at lower elevations will be particularly reactive.
  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely - Very Likely
    Dimensione
    1–5
    Some areas may have 50 cm of recent storm snow. SW winds have built fresh windslabs in lee features and behind ridgecrests. Warm temperatures have promoted rapid settlement and slabbing in open areas. Wet Slabs are possible at lower elevations.

Avalanche Summary

Avalanche activity has picked up over the last couple days with the increase in load and temperatures. Many loose wet avalanches up to size 2.0 have occurred below treeline, where the recent precipitation has fallen as rain. Higher in the terrain both explosive and rider controlled triggering has been observed, predominantly in wind loaded areas. A single, large, cornice triggered natural was reported  (size 3.0) on a north facing slide path in the Bear Pass region.

Confidence

Fair - Due to limited field observations

Weather Forecast

Monday: Expect a lull in the storm activity, with cloudy skies, light variable winds and alpine temperatures reaching -6. No precipitation.Tuesday & Wednesday: Several weak disturbances should make their way across the region, giving isolated bursts of precipitation under consistent cloudy skies. Expect light to moderate southerly winds and alpine temperatures should reach -5 each afternoon.

Snowpack Summary

Up to 40mm of water equivalency has fallen in the past 24-36hrs. Below 1000m, much of this precip has fallen as rain and we have reports in some areas that the upper 50cm of the snowpack is rain soaked. Above 1000m, the new snow is settling rapidly. Windslabs are forming in lee zones and behind ridges with the consistent SW winds. Cornices are growing rapidly under the current condition.A thin melt-freeze crust buried on January 17 is widespread at lower elevations. The combo of rainsoaked surface snow and this slick sliding layer may magnify the loose sluffing at lower elevations in the short term.Lingering deeper (down 50-80 cm) sits a persistent weakness comprising of surface hoar and/or facets. Recent tests on this layer are showing both sudden and resistant planar results. We have also seen an extended column test at 30/100 (end) indicating the propensity for propagation if this layer were triggered.  Keep these layers on your radar in regards to distribution and reactivity. The mid and lower snowpack is generally well settled and strong, although basal facets remain a concern in the northern part of the region.

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