Avalanche Canada jlammers, Avalanche Canada

Sea to Sky Avalanche Forecast

Dec 20th, 2012 9:41AM

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

Weather intensity is uncertain for Thursday night and Friday. If snowfall amounts are heavy or if overnight winds are strong, avalanche danger ratings may go to High.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Overnight Thursday and Friday: Moderate snowfall on Thursday tapering-off to light on Friday with the possibility of ongoing moderate snowfall in the south of the region / Moderate to locally strong southeast winds / Freezing level at surfaceSaturday: Light snowfall with moderate accumulations in the south of the region / Light to moderate southeast winds / Freezing level at surfaceSunday: Light snowfall / Light southeast winds / Freezing level at surface

Avalanche Summary

Explosives control on Thursday produced storm/windslab avalanches to size 2. I would expect ongoing wind/storm slab avalanches if snowfall and wind persist.

Snowpack Summary

The region has received an impressive amount of new snow in recent days. The snowfall was accompanied by consistently strong to extreme winds that have since backed off leaving significant amounts of lower density snow over deeper windslabs.A couple of layers of surface hoar were buried last week in some areas. Test results on the surface hoar suggest an improving bond. A deeper layer of surface hoar from late November is now well over a metre down and no activity has been reported on this layer either. In general, the mid-pack is reported to be well settled and strong.  The early November crust/facet combination near the base of the snowpack seems to be dormant. Triggering one of these persistent weak layers has become unlikely; however, the consequences would be significant.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1 - 4
New snow and winds are likely to create ongoing widespread new snow instabilities on most aspects and elevations. Sluffing may also be encountered on steep terrain.
The new snow may require several days to settle and fully stabilize.>Be cautious of sluffing in steep terrain.>Be cautious as you transition into wind affected terrain.>

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Dec 21st, 2012 2:00PM