Avalanche forecast

Northwest Inland

Feb 12 – 13, 2015Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

We're still working with quite a bit of uncertainty regarding the region's snowpack structure after last weekends storm.  Avalanche danger may be higher than forecast in areas that see continued precipitation fall as rain on previously dry snow.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Several weak layers are lucking in the snowpack and slopes at and above treeline may have the potential to produce very large and destructive avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–4
    New snow may be sitting on isolated pockets of surface hoar. Moderate southerly winds will continue to load lee features. Reactive softslabs will be more widespread in the North where the snowfall amounts are expected to be greatest.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Warm temperatures and rain are saturating the snowpack at lower elevations. A breakable freezing rain crust might make for challenging travel in the South of the region

Confidence

Poor - Due to the number and quality of field observations

Weather Forecast

By the end of Saturday a series of frontal systems will have brought up to 35mm of precipitation to the northwest of the region and around 15mm to the area around Smithers.Rain is expected at lower elevations in the south.5-10 cm of snow is expected to have fallen in the alpine by Friday afternoon with the heavier snowfall concentrated in the north. The freezing level in the southern half of the region could be as high as 1500m but should remain close to valley bottom further north. Winds will be moderate from the southwest. Similar freezing levels are forecast for Saturday when northern regions could see another 5cm of snow with moderate southwest winds becoming westerly. A cooling and clearing trend is expected to begin on Sunday accompanied by light northwest winds.

Avalanche Summary

No new avalanche have been reported yet through this storm    At least one one avalanche last weekend on the early February surface hoar and I suspect that some of the bigger ones that were reported may have stepped down to even deeper week layers.  Given the uncertainty I would keep these layers in mind especially in areas that receive more snowfall through this system.

Snowpack Summary

Between 10 cm of new snow in the south of the region and 20cm in the north has fallen at upper elevations as of Thursday afternoon.  This may sit on a thin new layer of surface hoar that was reported to be growing in the lull between the last two storms.  A freezing rain crust may have formed on the surface at lower elevations. Deeper in the snowpack there are a number of weak layers although there is uncertainty about which of them are still players, and which are now dormant. The early-February surface hoar layer may not exist  everywhere, but where it does it can be found buried between 30 and 70 cm down. The late January crust is probably down 75 to 150cm in the south of the region but is likely shallower in the north. The mid-January rain crust and surface hoar is probably down between 100 and 200cm. Finally, the crust/facet combination from November is near the ground.

Regions covered