Bollettino valanghe

Kootenay Boundary

Feb 23 – 24, 2012Avalanche Canada
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Archiviato · scaduto 15 years ago

Pericolo valanghe

Sat
Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
Apri la mappa completa

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–6
    Strong gusty northwest winds have transported available new snow into thick wind slabs that are very easy to trigger. Many avalanches have been triggered by traveling near wind loaded slopes. Low angle terrain may also slide.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely - Very Likely
    Dimensione
    3–7
    A persistent weak layer (PWL) comprising surface hoar in sheltered areas, a crust on solar aspects and facets elsewhere lies buried 40-70 cm below the surface. This layer was buried on February 8th.

Confidence

Fair - Timing of incoming weather is uncertain on Friday

Weather Forecast

A low pressure system is moving inland from the coast on Friday. This system is forecast to bring snow and moderate southwest wind to the Columbia Mountains by early morning and to the Kootenay Boundary region by the afternoon. Snowfall amounts are forecast to be about 10 cm for the Purcells and 10-15 cm for the Kootenay Boundary on Friday. Another 10 cm for the Purcells and another 10-15 cm for the Kootenay Boundary are expected overnight and during the day on Saturday. Sunday is forecast to be a mixed bag of convective flurries and some sunny periods. The freezing level is expected to rise to about 700 metres on Friday, drop back to valley bottom overnight and then rise to near 1000 metres on Saturday.

Avalanche Summary

We are getting reports of more frequent and larger avalanches that are running on the Feb. 8th crust and/or buried surface hoar. Avalanches up to size 3.0 were reported from the control work at Kootenay pass along the highway corridor. Remotely triggered avalanches continued to be reported.

Snowpack Summary

About 10 cm on Wednesday night combined with the 10-15 from Tuesday night and strong gusty northwest winds have created widespread windslabs in open areas at all elevations. The snow from the past few days has added to the load which is sitting above the weak layers that developed during the early February drought. There is about 50-80 cm above these persistent weak layers (PWL) of crusts, surface hoar, and facets. Snowpack tests show that the slab above the PWL is sliding easily with sudden planar or sudden collapse characteristics. Professionals throughout the region are treating this layer with extreme caution, since it is showing signs of remote triggering and the ability to propagate in low angled terrain. In shallow snowpack areas concerns remain for the mid-December persistent weakness down around 80-100cm and for basal facets. Treeline snowpack depths are approximately 230 cm.

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