Lawinenlagebericht

Northwest Coastal

Mar 7 – 8, 2017Avalanche Canada
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Archiviert · abgelaufen 10 years ago

Lawinengefahr

Wed
Thu
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

It's time to dial back terrain choices at all elevations:  There is a lot of uncertainty surrounding the buried weak layer underneath the persistent slab. This interface has remained problematic longer than we'd typically expect in this region.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–3
    Storm snow from the last week has consolidated into a slab 50-85cm in depth that is poorly bonded to the old surface due to a persistent buried weak layer. These slow to heal slabs are most likely to be triggered in wind exposed terrain.

Confidence

Moderate - The weather pattern is stable

Weather Forecast

We're looking at occasional flurries and then cold and clear toward the end of the forecast period. WEDNESDAY: Flurries with 5-10 cm of new snow, 20-30 km/h east winds, alpine temperatures around -12 C. THURSDAY: Cloudy with scattered flurries and up to 3-5 cm of new snow, 30-50 km/h east winds, alpine temperatures around -16 C. FRIDAY: Sunny with cloudy periods, 20-40 km/h southeast winds, alpine temperatures around -16 C.

Avalanche Summary

On Monday two avalanches were simultaneously remote-triggered below treeline west of Terrace. See here for the excellent details in the Facebook post.  Crown heights were 50-80cms.We had reports of two rider-triggered wind slab avalanches (Size 1.5 and 2.0) southwest of Terrace on Sunday. In both cases the crown height was 50cm and shooting cracks were also reported in mellow terrain. There was a remote-triggered Size 1 in the Shames backcountry, also with a 50cm crown, running on a weak facet layer.On Saturday several storm slabs sized 1.5 to 2.5 (some remote triggered) were reported on north through east aspects, between 1100 and 1400m elevation.Conditions will remain touchy as the recent storm snow settles and stiffens.

Snowpack Summary

We've had 5-10cm of low density snow falling for each of the past few days, which has brought recent storm snow totals to 70-100 cm. All this snow has buried a variety of old snow surfaces including surface hoar, facets, crusts, stiff wind slabs and a melt-freeze crust below 1600 m. The storm snow remains very reactive on this interface, resulting in widespread whumpfing and cracking in flat terrain. Moreover, we've had reports of sudden, propagation-likely test results down 50-85 cm on weak facets or the late-February crust / surface hoar.Below this interface the snowpack is generally settled and strong with the exception in shallow snowpack areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern.

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