Avalanche forecast

Northwest Inland

Feb 10 – 11, 2015Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Another pulse of new snow will be accompanied by strong to extreme winds re-elevating avalanche hazard.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    4–7
    Several weak layers are lucking in the snowpack and slopes at and above treeline still may have the potential to produce a very large and destructive avalanches. Smaller surface avalanches may step down to these deeper instabilities.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    New snow will fall on surface hoar in many locations. Forecast southerly winds of up to 100km/h will rapidly load lee features. The new snow may also stress older storm instabilities that have not yet had a chance to fully stabilize.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

A trough of warm air aloft will linger over the region Wednesday before a series of fronts hits the North Coast forcing the arctic air to retreat north. Wednesday will see 5-10cm of new snow accompanied by strong to extreme southerly winds. Snow will continue through the rest of the forecast period with up to 10cm expected on Thursday, followed by another 10cm on Friday. Winds will remain strong from the south. Freezing levels will climb through the week reaching 2000m by Friday.

Avalanche Summary

We haven't received any repots of new avalanches in the last couple of days and over the weekend we received only a few observations. It sounds like most of the weekends avalanche activity was limited to mid-storm instabilities although at least one ran on the early February surface hoar. I suspect that some of the bigger ones likely stepped down to deeper week layers, but thats just a guess.

Snowpack Summary

New snow will fall on fresh surface hoar and a sun crust on steep south aspects. Since the beginning of February the region has received 30 to 70cm of dry low density snow accompanied by strong to extreme winds out of the E through SE. Bellow this there are a number of weak layers in the region's snowpack. Right now there's a lot of uncertainty about which layers are still players, and which have gone dormant. The early February surface hoar lies under the recent storm snow but little is known about its distribution. 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 which may feature surface hoar on top in some locations is probably down between 100 and 200cm. Finally, the crust/facet combination from November is near the ground. Basically, it's not a very easy snowpack to work with and we'd appreciate any observations shared via the Mountain Information Network.

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