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Archived

Avalanche Forecast

Feb 21st, 2012–Feb 22nd, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Northwest Inland.

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

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.

Avalanche Problems

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

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