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Avalanche Forecast

Archived

Nov 28th, 2012–Nov 29th, 2012

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

South Coast.

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

A deep low pressure system off the Gulf of Alaska will be bringing a very moist, warm and active weather pattern over the next five days. The system will move into the region Wednesday afternoon, and persist with moderate to heavy amounts of precipitation through the weekend. Thursday: FLVL’s 1400 m, snow amounts up to 25 cm, ridegtop winds SE 40-50 km/hr, alpine temps -4.0.Friday: FLVL’s 1500 m, snow amounts 15-25 cm, ridgetop winds SE 60-gusting 80 km/hr, alpine temps -3.0.Saturday: FLVL’s 1400 m falling 1000 m overnight, 5-10 cm, ridgetop winds S 20 km/hr, alpine temps -3.0.

Avalanche Summary

Check out Wayne Flann's Avalanche Blog for a photo of a recent large avalanche off the north face of Mt. Currie. Natural avalanche activity will pick up again with forecast wind and snow.

Snowpack Summary

New storm slabs will build over a variety of weak snow surfaces. These surfaces consist of large surface hoar, a thin sun crust, surface facets, moist snow, or preserved storm snow depending on elevation, sun and wind exposure, slope angle, time of day, and aspect. The main snowpack feature is a rain crust buried early November and now down around 60-80 cm at treeline. A weak layer of facets sitting on top of this crust shows "sudden" fracture character and the ability to propagate into large avalanches if triggered. Widespread whumpfing and cracking on this layer has also been reported. It's mostly a concern at upper treeline and alpine elevations on slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, grass, etc.). Coquihalla Pass and Cayoosh Pass have around 50cm on the ground at the road elevation. Treeline areas have around 100-120 cm Alpine areas likely have more snow, but also highly variable depths depending on wind exposure. For more information check out the telemarktips.com forum, the Mountain Conditions Report, and Wayne Flann's Avalanche Blog.

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.

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.