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Avalanche Forecast

Archived

Mar 30th, 2014–Mar 31st, 2014

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

Regions

Northwest Coastal.

Prolonged sun exposure may initiate natural avalanche activity, especially on south through west facing slopes.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Synopsis: A ridge of high pressure over the NWT continues to advance south. Looks like continued cool and dry conditions for the NW for the forecast period. The models show an organized system that approaches the north coast Wednesday/Thursday, check back tomorrow for more details. Monday: Freezing Level: 800 - 1300m; Precipitation: Nil; Wind: Treeline: Light, NW | Ridgetop: Light, NWTuesday: Freezing Level: 600 - 1300m Precipitation: Nil; Wind: Treeline: Light, SW | Ridgetop: Moderate, WWednesday: Freezing Level: 400m - 1300m; Precipitation: Trace; Wind: Treeline: Light, S | Ridgetop: Moderate, SW

Avalanche Summary

No avalanche observations from Saturday.On Friday loose snow was sluffing to size 1, several sluffs initiated thin size 1 slabs running on an old suncrust. There was a second hand report of a skier triggered size 2 avalanche at treeline that resulted in the skier going for a ride. Sounds like everyone made it out okay, and that the folks involved will head back later in the spring to find their lost gear. If you were part of this incident, we'd love it if you'd fill out a report. Thanks!

Snowpack Summary

Strong Easterly winds have been reported to have caused intense wind transport of the recent storm snow, developing pockets of wind slab on various aspects in the alpine and at treeline. Forecast cool temperatures are not expected to promote much settling or bonding of the near surface layers, and probably not much change to the persistent weak layers. The deeply buried persistent weak layers continue to provide moderate to hard sudden planar results in snow profile tests, but may be deep enough to require a heavy load for triggering. The March weak layer is a combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects. This layer is widespread throughout the forecast region and is now buried close to 150cm in most parts of the area. A late January/early February crust/facet/surface hoar combo is now buried 200 cm or more.

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.

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.