Avalanche forecast

Northwest Inland

Feb 3 – 4, 2013Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    New snow and strong shifting winds has built touchy wind slabs that are likely found behind terrain breaks such as ridges and ribs. Hollow sounds and cracking snow is a good indicator of unstable snow.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Buried beneath the new snow sits a surface hoar/crust/facet weakness. This may be sensitive to rider triggers in steeper sheltered terrain or over convex rolls, especially at treeline and below treeline elevations.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–6
    A deeply buried weak layer near the base of the snowpack could be triggered by large loads such as a cornice collapse or from a thin-spot trigger point.

Confidence

Fair - Due to limited field observations

Weather Forecast

Monday: Expect lingering clouds and light variable winds with alpine temperatures reaching -6. No precipitation.Tuesday & Wednesday: Some weak disturbances may penetrate inland to give isolated snowshowers with limited accumulations. Winds should remain light and southerly and temperatures should reach -5 each afternoon.

Avalanche Summary

Isolated windslabs up to size 2.0 have been controlled at ridgecrest and loose wet sluffing has been observed below 1200m due to the persistent warm temperatures.

Snowpack Summary

Touchy wind slabs have built on lee slopes and behind terrain features likes ribs and ridges. Up to 50 cm of new snow has buried a variety of old surfaces including old wind slabs, scoured thin slopes, crusts and surface hoar. This interface has shown isolated reactivity to rider triggering, especially around treeline and below treeline elevations. Warmer temperatures have promoted some settlement and consolidated the recent snow into slab-like characteristics. With little observations from the field it's hard to get a good handle on how widespread this layer is, so I would  stress the importance of digging down to find and test weak layers. A cautious and curious approach is critical.The average snowpack depth at treeline is near 100 cm but remains quite inconsistent across the region. A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.

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