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Avalanche Forecast

Archived

Feb 13th, 2014–Feb 14th, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Little Yoho.

Avalanche conditions are `touchy` and the overall hazard is on the rise. Expect this trend to continue through the weekend. SH

Weather Forecast

Light gusting strong Westerly winds and 5cm forecast for Friday. 5cm on Sat then up to 20 cm with strong winds for Sunday. We expect the hazard to slowly increase during the weekend. Temperatures will be mild.

Snowpack Summary

Treeline storm snow amounts are 50cm in Kootenay and Yoho,35cm in the Sunshine area, and 20cm in the Louise/Hwy 93N areas. Winds,warm temps causing slab development in exposed areas,which overlies a complex layer of facets, surface hoar and sun crust on solar aspects. Below this a generally well settled midpack overlying the basal depth hoar layer.

Avalanche Summary

Field trip to Kootenay saw numerous naturals at all elevations to size 2.5 occur within the last 24 hrs. Forecasters were able to ski cut size 2`s which were low density slabs along ridgetops on the Jan 30th surface hoar. These were running 100-300m and were on average 30-40cm deep. Smaller slides were observed in other areas with less storm snow.

Confidence

Due to the number and quality of field observations on Thursday

Problems

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.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.