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Avalanche Forecast

Archived

Feb 18th, 2015–Feb 19th, 2015

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

Regions

Northwest Inland.

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Confidence

Fair - Due to the number of field observations

Weather Forecast

A weak pacific frontal system will bring light snowfall (between 5 and 10cm) Wednesday night and into Thursday. A clearing trend is forecast for Friday and Saturday as a ridge of high pressure rebuilds in the eastern Pacific. Winds are expected to be strong from the southwest on Thursday, and then become moderate from the northwest on Friday and Saturday. Daytime freezing levels should hover around 1000m for the forecast period

Avalanche Summary

Sometime during the last few days, a natural cornice fall triggered a large slab avalanche in steep, rocky alpine terrain near Smithers. (see the latest Mountain Information Network post for pictures and more details) Loose wet avalanches to size 1.5 were also noted on Tuesday in response to warming and solar radiation. There will likely be a shift to new wind slab activity with snow and wind forecast for Thursday.

Snowpack Summary

In general, snow surfaces are highly variable. In the south of the region, melt freeze conditions exist below about 1800m. Above this you'll likely find settled wind slabs on north facing terrain, and a melt freeze crust on solar aspects. Between 15 and 40cm below the surface you may find weak surface hoar which was buried on February 10th. Although recent warming may have destroyed this potentially weak layer in some areas, I'd dig down and test for this layer at upper elevations where colder temperatures may have allowed for this weakness to persist. In general, the mid snowpack is strong and well-settled, and at the base of the snowpack, facets which formed earlier in the season have gone dormant for the time being. Cornices are reported to be large and unsupported.Further north in the region, slightly cooler temperatures have persisted and melt freeze conditions are not as widespread. In these areas deeper persistent weaknesses are more likely to exist.

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.