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Archived

Avalanche Forecast

Nov 28th, 2012–Nov 29th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

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.

Avalanche Problems

Storm Slabs

New snow will build storm slabs on all aspects, overlying a variety of weak surfaces. Storm slabs and new wind slabs will be touchy, and natural avalanche activity is likely.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Persistent Slabs

Slopes with smooth ground cover and reloaded bed surfaces. Prone to remote triggering and step down avalanches. Typical trigger points include thin rocky areas. May be difficult to trigger, but often very large with serious consequences.
Be aware of thin areas that may propagate to deeper instabilites.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 5