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Avalanche Forecast

Archived

Nov 24th, 2012–Nov 25th, 2012

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

There is just enough load on the November 6 crust which is down approximately 40-60 cm to become a danger for triggering. Use caution and avoid very steep lee slopes particularly just at treeline. JBW

Weather Forecast

The forecast calls for mainly sunny weather over the next few days with high pressure ridging and some convective showers. The main storm energy will be to the south. The winds will be westerly and still moving snow

Snowpack Summary

Up to 60 cm storm snow over the past 5 days has settled into a soft slab approximately 30-40 cm thick. In open areas wind has blown the storm snow into a soft slab with wind slabs on north and east aspects. Nov. Cr down 40-60 now.

Avalanche Summary

Several Na out of steep terrain in the alpine during the storm up to size 2.5, some failing on Nov. Cr and some on storm snow. Avalanche control today produced up to size 2 slabs as much as one metre deep in lee areas.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.