Avalanche Forecast

Issued: Dec 16th, 2013 7:56AM

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

Peter, Avalanche Canada

South Columbia.

Forecast snowfall amounts could vary across the region. Southern and western parts of the region could see considerably less snow, potentially resulting in lower avalanche danger. Be sure to make careful local observations.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Tonight and Tuesday: A warm front moves through tonight bringing generally light precipitation, followed by the trailing cold front on Tuesday with stronger precipitation. Expect accumulations of up to 20 cm in some areas. The freezing level is around 900-1100 m and winds are strong to extreme from the SW-W.Wednesday: Precipitation should taper off with gradual clearing throughout the day. Temperatures drop with the freezing level returning to valley bottom by evening. Winds ease to light or moderate from the NW. Thursday: Mainly sunny and cooler. The freezing level should be at valley bottom with moderate northerly winds.

Avalanche Summary

Parts of the region reported a fairly large natural avalanche cycle late Saturday through Sunday morning, with several avalanches up to Size 3. Skier testing also produced a few avalanches up to Size 2, primarily in wind loaded terrain or on very steep convex rolls.

Snowpack Summary

Although recent accumulations have been highly variable, up to 60cm of snow now overlies the weak faceted crystals or small surface hoar which formed during the last cold snap. Rising temperatures are reported to have enhanced slab properties creating a more reactive "upside-down" snowpack, especially at lower elevations. Moderate to strong southwest winds have created dense wind slabs in exposed high elevation terrain.As of late there has been no reported activity on the late-November interface which consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. This layer, buried between 60-80cm below the surface, is generally considered to be "stubborn" to trigger; however, avalanches at this interface could have nasty consequences.

Problems

Wind Slabs

Forecast new snow and strong to extreme westerly winds will likely create dense new wind slabs in exposed lee terrain at all elevations. These wind slabs may release naturally in specific areas.

Be cautious as you transition into wind affected terrain.>Avoid avalanche terrain during periods of heavy loading from new snow and wind.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Continued loading and mild temperatures could make buried persistent weaknesses in the upper and mid snowpack much more reactive. Make conservative terrain choices over the next couple days.

Make observations and assess conditions continually as you travel.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Valid until: Dec 17th, 2013 2:00PM