Avalanche Forecast

Issued: Feb 20th, 2012 8:50AM

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

Avalanche Canada pmarshall, Avalanche Canada

With a bit more wind and snow and slightly milder temperatures we could reach "the tipping point" very soon. Check out the latest post in the Forecaster's Blog for more information.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Tonight and Tuesday: Moderate snowfall - 5-10cm tonight and an additional 10-15cm tomorrow. Winds increase to moderate-strong from the west. The freezing level (FL) is near valley bottom tonight rising to 1200m on Tuesday. Wednesday: Continued light to moderate snowfall - 5-10cm. FL dropping to 800-1000m. Winds should be moderate-strong from the west-northwest. Thursday: Cooler and drier under a brief ridge of high pressure. FL dropping to around 500m.

Avalanche Summary

There are several reports of natural and skier triggered avalanches up to Size 1.5. These avalanches occurred in wind affected terrain in the alpine, or on steep convex shaped features below treeline. The size and likelihood of avalanches will increase as the new snow settles into a more cohesive slab.

Snowpack Summary

Wind slabs continue to grow in exposed terrain in response to moderate W-SW winds. 15-40cm of low density snow overlies the Feb. 9 weakness, which includes surface hoar and/or a crust. This surface hoar layer may be widespread in some areas, while others have reported it being confined to shady aspects at treeline and in the alpine. A melt-freeze crust has developed on solar aspects at all elevations, and on all aspects below about 1600 metres. The mid-pack is generally well settled. There is some concern that large loads like cornices may trigger the Jan. 20th facet layer. Some shallow snowpack areas may continue to have a weak layer of basal facets near the ground.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs are building in exposed leeward terrain and may be susceptible to human triggering.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Up to 60cm of storm snow has started to settle into a soft slab and sits on several weaknesses including surface hoar. The size and likelihood of natural and human triggered avalanches will increase throughout the forecast period.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Feb 21st, 2012 8:00AM