Avalanche Forecast

Issued: Dec 7th, 2013 8:29AM

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

Avalanche Canada bcorrigan, Avalanche Canada

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Sunday is forecast for cold temps with an increase in outflow winds, especially at upper elevations.  Monday: No change in sight for the next few days as the Arctic ridge of high pressure continues to dominate through the next week. Sunny skies and cold temperatures are forecast. Alpine temperatures should hover around -20., with -15 in the valley bottoms. Winds will be light to moderate from the north.  A pacific frontal system will move onto the coast on Wed. or Thursday next week.  Timing and precipitation amounts are uncertain at this time.

Avalanche Summary

No recent reports of avalanches. Storm slab avalanches may be triggered by additional loads like skiing/riding. These avalanches may be large and destructive. The forecast cold temperatures will slow down bonding processes and promote surface facetting and surface hoar growth in protected locations

Snowpack Summary

Wind slabs are sitting above recently buried weak layers of surface hoar on North aspects with melt/freeze crusts on solar aspects. The storm slab is still producing moderate shears on the surface hoar between 40 and 50 cm down. This slab is not well consolidated in many parts of the region and may not produce shears in snow pit tests. Widespread whumpfing has been observed in the Nelson area from tree line elevations all the way to valley bottom. There are reports of a deeply buried early season crust that formed in October, this layer is more likely to be found in the high alpine on northerly aspects.Surface facetting continues and new surface hoar growth is being reported in some areas. This will be something to watch when the weather pattern finally changes.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs are being created by N-NE winds at ridge tops and tree line. The surface hoar from late november may become quite reactive as the storm slab strengthens. The possibility of a large destructive avalanche is still out there.
Be careful with wind loaded pockets. Be aware of wide variation in snowpack depth>Be cautious as you transition into wind affected terrain.>Avoid travelling in areas that have been reverse loaded by winds.>The best powder will be found in sheltered locations at or below treeline.>

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 8th, 2013 2:00PM

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