Avalanche Forecast

Issued: Dec 5th, 2012 10:07AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight and Thursday: Light snowfall / strong west winds decreasing to moderate and southwest by Thursday / Freezing level at 800mFriday: Light snowfall / moderate to strong southwest winds / Freezing level at surface  Saturday: Trace amounts of snow / Light north winds / Freezing level at surface

Avalanche Summary

On Wednesday several natural avalanches to size 2 were reported from the region while explosives control produced isolated releases to size 2.5. These releases which occurred at treeline and above are suspected to have run within recent storm/wind layers or on the late November surface hoar.

Snowpack Summary

Recent snowfall amounts have been highly variable, but in deeper snowpack areas up to 85 cm of settled storm snow has fallen in the past week. This snowfall was accompanied by generally moderate to more recently strong and variable winds, forming deep and reactive wind slabs in exposed leeward terrain. Below the recent storm snow is a layer of surface hoar that was buried at the end of November. This layer continues to be reactive. At the base of the snowpack sits the early November rain crust. This layer seems most likely to be found in deeper snowpack areas at higher elevations. I'm not aware of any activity on this layer as of late, but observations have been limited and it may have the potential to 'wake-up' with continued loading.There are significant variations in snowpack structure from one drainage to another. In short, digging down and making your own observations will be critical to safe slope selection. Thank you to those who have shared field observations with us. If you would like to do the same, you may contact us at forecaster@avalanche.ca.

Problems

Storm Slabs

An icon showing Storm Slabs
In some areas relentless snowfall and wind has created an ongoing wind/storm slab problem. Watch for triggering in gullies, below ridge crests and behind terrain features.
Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
A layer of surface hoar buried at the end of November has been responsible for fairly widespread avalanche activity in some areas. Where it exists, this layer may persist for quite some time.
Be aware of the potential for large avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

1 - 6

Valid until: Dec 6th, 2012 2:00PM