Avalanche Forecast

Issued: Dec 6th, 2013 8:39AM

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.

bcorrigan, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Saturday: The forecast is for Saturday to be the coldest day of this arctic outbreak with temperatures beginning to slowly rise early in the week.Sunday: Sunday is forecast for cold temps with an increase in outflow winds, especially at upper elevations.No change in sight for the next few days as the Arctic ridge of high pressure continues to dominate through the weekend and into the beginning of next week. Sunny skies and cold temperatures are forecast, with Saturday being the coldest in the forecast. Alpine temperatures should hover around -20., with -15 in the valley bottoms. Winds will be light to moderate from the north, with stronger winds forecast for Sunday.

Avalanche Summary

No recent reports of natural avalanches. Storm slab avalanches may continue to be triggered by light additional loads like skiing/riding. These avalanches may be large and destructive. The snowpack needs more time to settle and bond . The forecast cold temperatures will slow down this process and preserve recently buried weak layers. This is a complex avalanche forecasting scenario; complicated by early season timing when we have few observations coming from the field.

Snowpack Summary

A dusting of new snow covers 40-70 cm of previous storm snow. Storm 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 not well consolidated in many parts of the region and may be not produce shears in snow pit tests. Widespread whumpfing has been observed near Nelson from treeline 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

Northeast winds have transported storm snow onto S and SW slopes, not a typical loading pattern. Be cautious of all wind loaded features

The best powder will be found in sheltered locations at or below treeline.>Avoid travelling in areas that have been reverse loaded by winds.>Be cautious as you transition into wind affected terrain.>Be careful with wind loaded pockets. Be aware of wide variation in snowpack depth>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Surface hoar from the end of Nov. is now buried by the recent wind slabs.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 7th, 2013 2:00PM