Avalanche Forecast

Issued: Feb 21st, 2012 9:54AM

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

Avalanche Canada swerner, Avalanche Canada

Please check out the new Forecaster's Blog for more detailed information on incremental loading, and "The Tipping Point"

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Light-moderate amounts of snowfall are expected Tuesday night into Wednesday morning. Ridgetop winds from the West near 75km/hr overnight, tapering off to 40km/hr from the NW on Wednesday. Thursday may bring some flurries, but mainly dry, cooler conditions with the associated ridge. Freezing levels will remain at valley bottom. Friday brings light snowfall, and changing moderate winds from the East.

Avalanche Summary

No new avalanches have been reported.

Snowpack Summary

About 20 cm of snow that fell over the past week sit on a variety of old surfaces. These surfaces include: melt-freeze crusts that exist on all aspects at lower elevations and on south-facing slopes higher up and well-settled powder on shaded aspects in the alpine. Weak surface hoar crystals (size 3-4mm) are sandwiched between the old surfaces and the newer snow and have recently shown easy compression test results. The distribution of the surface hoar seems to be up to treeline on all aspects and on sheltered features in the alpine. This upper snow pack structure will be the big thing to watch as the overlying slab develops. I expect to see gradually increasing reactivity in the surface hoar interface with incremental loading and higher winds forecast for this week. Check out our Forecaster's Blog for some insight on incremental loading and the "Tipping Point" The mid and lower snowpack are generally well settled and strong.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Forecast snow and wind will increase the soft slab load on the variable buried weak layers. I suspect this to be a concern as these layers reach their "Tipping Point" where natural and human triggered avalanche activity will increase.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Wind Slabs

An icon showing Wind Slabs
Increasing winds and new snow through the forecast period will form wind slabs on lee slopes and terrain features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Feb 22nd, 2012 8:00AM