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Avalanche Forecast

Archived

Dec 25th, 2013–Dec 26th, 2013

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

Regions

Little Yoho.

The basal depth hoar can be heard jing, jing, jingling in your snow pit. Conservative terrain choices are important to stay safe when dealing with this overall weak snowpack. Happy holidays. SH

Weather Forecast

The very windy alpine conditions will continue Thurs and Fri. with strong to extreme westerlies. Light snow amounts of 5-10cm expected over the next 2 days and freezing levels to valley bottom.

Snowpack Summary

5-10cm of new snow in the W tapers to nothing in the E. A variety of surface weaknesses including widespread windslabs in the ALP and isolated surface hoar at TL & BTL sit on a generally weak snowpack. The real concern is the facet/depth hoar/crust combo at the base of the snowpack which been triggered by light loads recently and can't be trusted.

Avalanche Summary

A size 2.5 was observed 2 days ago on a N aspect of Mt. Fairview. It was initiated as a wind-induced spindrift avalanche which pulled out a slab that failed near the ground. This is indicative of the widespread basal weakness present in the snowpack.

Confidence

Due to the quality of field observations on Wednesday

Problems

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.

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.