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Avalanche Forecast

Archived

Dec 10th, 2012–Dec 11th, 2012

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

South Coast.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Overnight and Tuesday: 3-5 mm of precipitation is forecast to start Monday evening and then end in the morning. Very Strong Westerly winds are expected overnight and during the morning. The ridge top temperature should be -8.0 and the freezing level at 1200 metres.Wednesday: Light variables winds in the morning should become moderate Northerly in the afternoon. Freezing level should drop down to the valley overnight and then rise to 800 metres during the day. No precipitation forecast.Thursday: Another frontal system is lining up to hit the North Coast on Thursday and then starts to move down to the South. Timing is unsure for this system.

Avalanche Summary

Evidence of previous avalanches up to size 3.0 from Mt Joffre at 2000 metres. Ski cutting produced heavy sluffing.

Snowpack Summary

It sounds like the wind started to transport the light surface snow into wind slabs in the alpine and at treeline. There isĀ  about 140 cms below treeline in the Duffey Lake area, with 30 cms ski penetration and waist deep foot penetration at treeline. At 1900 metres on a NE aspect there was 60 cms of very light (Fist) density snow above slightly stiffer (4 Finger) snow. Snow stability tests showed only mid storm collapses. The Coquihalla also has a well settled "right side up" snowpack that is about 190 cms deep at 1550 metres elevation. "Right side up" means that the surface layers are light and soft, and then the layers get progressively more dense as you move down through the snowpack. The ski penetration has been reported to be about 40 cms and the foot penetration is very deep at 80 cms. The light snow is causing a lot of sluffing in steeper terrain, but is not reacting as a slab. The November crust has not been found in the Coquihalla, although we don't have any reports from the high alpine. Conditions may be quite different in the North of this region, please email us your observations if you are out in the field. [email protected]

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.