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Avalanche Forecast

Archived

Feb 12th, 2014–Feb 13th, 2014

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

Regions

Little Yoho.

Small natural cycle occurring in the alpine.  Very touchy wind and storm slab condition exists.  It's definitely time to pick more conservative lines or routes.

Weather Forecast

Another 5 cm forecasted for Thursday and 5 for Friday with moderate to strong SW winds is forecasted for the next few days.

Snowpack Summary

A touchy 15-30 cm soft wind/storm slab is not bonding well to underlying surfaces (surface hoar, facets, and suncrust) formed from the past three weeks of cold, dry weather. With additional snow forecast over the next few days, expect the soft slabs to increase in depth and size.

Avalanche Summary

A natural cycle was occurring in the alpine, but visibility was poor. Across the region, several soft touchy windslabs 15-30 cm deep (size 1.5) have been ski cut on all aspects above treeline. Propagations were generally 10-40 m. A general observation was small avalanches were running far an fast, up to 700 m in one case in KNP.

Confidence

Due to the quality 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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.