Avalanche Forecast

Issued: Nov 29th, 2012 8:39AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada triley, Avalanche Canada

The timing of this storm is suspect. If you are seeing more precipitation than forecast in your area on Friday, then consider these danger ratings to be a bit low.

Summary

Confidence

Fair - Due to limited field observations for the entire period

Weather Forecast

Overnight Thursday: Freezing levels are expected to continue to rise on Thursday evening up to about 1600 metres and should be combined with moderate SW winds and light precipitation. During the overnight period, expect freezing levels to move down to about 1200 metres combined with continued moderate SW winds and precipitation increasing to moderate ( 10-15 mm for the Fernie Area, and about 10 mm further East). Friday: Freezing levels should rise a little bit during the day as waves of light to moderate precipitation continue ( 5-10 mm total during the day). SW winds are expected to continue in the alpine.Saturday: The freezing level should start to drop down to near the valley bottoms after a cold front moves through to the East. Alpine winds should continue to be moderate from the SW. Poor confidence in precipitation amounts and timing for Saturday and Sunday.

Avalanche Summary

No recent avalanche observations.

Snowpack Summary

Surface conditions vary throughout the region. You might find surface hoar, a light zipper crust or something entirely different depending on what drainage you're in.  You need to know what the weekends snow is falling on before committing to a line.  Start by going small this weekend & remember that the storm slab has the potential to behave in very different manors depending on what aspect & drainage you're in.  This is a very young snowpack, don't take your eyes off it.  Alpine snow depths are somewhere between 1 - 2 m. Depths quickly drop below threshold near treeline. An early season rain crust exists from rain events in late Oct./early Nov. Wind exposed terrain at and above treeline features old isolated wind slabs that range from 50 - 100 cm in depth.

Problems

Storm Slabs

An icon showing Storm Slabs
Old wind slabs may continue to linger on steep slopes that are not well supported by the terrain below. These windslabs are likely to be buried by new storm slabs in the next few days. Storm slabs may take a few days to bond to the old surface.
Avoid shallow snowpack areas where triggering is more likely.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
We have not heard of any new releases on this early season rain crust. The new storm snow may create enough of a load to activate this layer. Look for signs of deep releases on steep terrain in the alpine during the storm.
Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Nov 30th, 2012 2:00PM

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