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Avalanche Forecast

Archived

Feb 25th, 2017–Feb 26th, 2017

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

Regions

Lizard-Flathead.

Updated @ 09:30 Sunday: Significant overnight snowfall will make excellent fodder for wind and storm slabs. Evaluate each slope carefully and stay out of the wind today.

Confidence

Low -

Weather Forecast

SUNDAY: Flurries overnight Saturday through Sunday, accumulation 10-20cm possible/ Alpine temperature -7 C / Light east windMONDAY: Isolated flurries, accumulation 5-10cm possible Sunday night into Monday morning / Light to moderate west wind / Alpine temperature -8TUESDAY: Mix of sun and cloud / Light to Moderate west wind / Alpine temperature -9More details can be found on the Mountain Weather Forecast.

Avalanche Summary

Explosives control near Fernie resulted in a deep persistent avalanche on Friday; this avalanche was size 2.5 on a north aspect at 2000 metres, and is believed to have released on the mid-December facets. There was a report on Tuesday of a natural avalanche size 3.5 on Mt Hosmer on an East aspect at 2100 metres that appears to have released on or stepped down to the weak deep persistent layer of sugary facets near the ground. On Wednesday we had a report of a size 3.0 avalanche on "Big Steep Mother" bowl on a northeast aspect at 2100 metres in the alpine in the Lizard range. This avalanche appears to have been started by a cornice fall that released a storm slab that then "stepped down" to deeply buried weak facets.

Snowpack Summary

20 to 40 cm of storm snow from Saturday night now rests upon the 50 to 60 cm of storm snow from last week. This 70 to 100 cm is likely settling into a storm slab in sheltered locations, and is almost certainly forming a wind slab in wind affected terrain. This slab sits above a thick rain crust below 1900 m and a generally well settled snowpack. Isolated basal weaknesses may still exist in shallow snowpack areas. These weak areas appear to be on north-northeast aspects in the alpine. If the winds shift direction over the next few days, watch for new wind loading on south-west aspects.

Problems

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.