Avalanche Forecast

Issued: Feb 19th, 2013 10:13AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Wednesday: Mix of sun and cloud / Light southwest winds / Freezing level at 700mThursday: Light snowfall intensifying in the evening / Moderate southwest winds / Freezing level at 900mFriday: Heavy snowfall / Moderate south winds / Freezing level at 800m

Avalanche Summary

Natural wind slab avalanches up to size 2.5  were reported from north to west aspects at treeline and above in the Blue River North area. As well, a size 2.5 natural slab avalanche released on a south face at 2400m. It is thought to have released on the February 12th interface.

Snowpack Summary

Variable amounts of new snow continue to add to the recent storm slab which sits above the February 12th weak surface hoar layer and a sun crust on solar aspects. This layer is now buried down about 30-70 cms depending on where you are in the region. New wind slabs developed at treeline and above due to the new snow and wind during the storm. These soft new wind slabs (hard slabs in some areas) are reported to be reactive and may be hiding stiffer wind slabs that are a couple of days older. Deeper persistent weak layers from early February and late January continue to show planar failures when moderate to hard forces are applied to snow profile tests. These deeper layers have not been reactive to the loads associated with recreationalists, but they may be triggered by large loads like an avalanche in motion, or a cornice fall.

Problems

Storm Slabs

An icon showing Storm Slabs
The storm slab is expected to continue to be sensitive to skiers and sledders.  Forecast warming on sun-exposed slopes may increase the sensitivity of the weakness where the storm slab overrides a crust.
The new snow will require several days to settle and stabilize.>Avoid sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wind Slabs

An icon showing Wind Slabs
Lingering wind slabs may take a couple of days to settle and bond.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
There are older layers of buried surface hoar and crusts that are buried down about 80-110 cms. These layers continue to show results in snow profile tests and may be triggered by large additional loads.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 20th, 2013 2:00PM