Avalanche Forecast

Issued: Feb 27th, 2012 9:31AM

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

Avalanche Canada swerner, Avalanche Canada

The snowpack is tricky to predict at the moment. Backcountry travel requires local knowledge, extensive experience and training. Please read the new Forecaster's Blog Post.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Tuesday: Mainly unsettled conditions, few flurries. Ridgetop winds 15km/hr from the South. Treeline temperatures near -9. Wednesday: Light snow amounts near 5cm. Ridgetop winds 30km/hr from the East. Treeline temperatures near -12. Thursday: Isolated flurries. Ridgetop winds 30km/hr from the SW. Treeline temperatures near -8.

Avalanche Summary

Natural ice and cornice fall has been reported. The natural ice triggered a size 2.5 on a NE aspect, while the cornice fall triggered a size 3.5 which ran to valley bottom. Reports of large loose power sluffing, entraining significant amounts of recent storm snow on N-NE aspects. West aspects also producing loose sluffing up to size 2. Many avalanches up to size 2.5 have been reported; both human and natural triggered. The smaller events released on storm interfaces while the bigger events went down to the February 09 facet/crust/surface hoar interface.

Snowpack Summary

Over the weekend new snow up to 25 cm fell. Generally, this has left us with a 45-60 cm sitting above the mid February layers. Recent clear, sunny skies have created a sun crust on south facing terrain into the alpine.The aforementioned mid February layers consist of a strong melt freeze crust below 1000m, buried wind slabs near treeline and higher into the alpine while between these elevations the interface varies wildly from facets, surface hoar, sun crust or wind press. The surface hoar seems to be spotty but is responsible for much of the recent avalanche activity. Recent testing done on the SH layers produced CTM SP down 70-100m. With the additional wind loading, pockets as deep as 90cm are possible on lee features. Recent outflow winds have exacerbated the wind slab issue, building reactive slabs on south facing terrain features. The mid and lower snowpack is generally well settled and strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Moderate winds and new snowfall have created new and reactive wind slabs on lee terrain. Recent outflow winds have compounded this problem with reverse loading.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The persistent interface from mid February remains a concern. Large avalanches occurred on Sunday, with these layers being suspect.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 6

Loose Dry

An icon showing Loose Dry
Large, loose dry avalanches have occurred within the recent storm snow entraining significant amounts of storm snow; especially from steep terrain features mainly on N-SE aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 28th, 2012 8:00AM

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