Avalanche forecast

Northwest Inland

Mar 12 – 13, 2017Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Warm stormy weather will elevate the danger on Monday. Very conservative terrain choices or professional-level training are recommended for any travel in avalanche terrain.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2
    A reactive slab has possibly formed above a weak layer of crusts, facets, and surface hoar that formed in February.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    20-40 cm of new snow will form fresh storm slabs that will be thicker, stiffer, and more reactive in wind affected terrain.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3
    A lingering weakness at the bottom of the snowpack may reawaken with the load of the new snow and warming.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY NIGHT: Storm continues with another 10-15 cm of snow, strong southwest winds, and climbing freezing levels.MONDAY: Another 2-5 cm during the day, strong southwest winds, freezing levels climb to about 1000 m with alpine temperatures around -2 C .TUESDAY: The next pulse brings 5-15 cm starting late Monday night, moderate southwest winds, freezing level dropping with alpine temperatures around -6 C.WENDESDAY: Lingering flurries with 2-5 cm, moderate southwest winds, alpine temperatures around -10 C.

Avalanche Summary

A MIN report from Friday describes a size 1 wind slab avalanche at Hudson Bay Mountain (here). A natural size 2 wind slab was also reported on a northeast aspect in the Howsons.On Monday, the new snow is expected to form reactive storm slabs and has the potential to awake persistent slabs above the weak February interface.

Snowpack Summary

Storm snow totals may reach 20-40 cm by Monday morning with deeper deposits in lee terrain. Rising temperatures will make reactive storms slabs. A weak interface that was buried in late February may finally have enough snow above it to form a reactive slab. The interface is composed of facets, crusts, and surface hoar that may be 40-80 cm deep. There's some uncertainty about the distribution and reactivity of this interface. A well consolidated mid-pack sits above weak basal facets (sugary snow) near the ground. The deeper basal weakness remain a concern in thin rocky start zones and shallow snowpack locations.

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