Avalanche Forecast

Issued: Mar 6th, 2013 9:40AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Loose Dry and Cornices.

swerner, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

As the low off the Oregon coast moves inland and South, light-moderate snowfall amounts are expected through Thursday. The low deteriorates by Friday morning and is being replaced by a ridge, bringing dry and sunny conditions with very little wind. Overnight into Thursday: Light-moderate snow accumulations. Ridgetop winds will blow light from the West. Alpine temperatures near -7 and freezing levels at 1500 m.Friday and Saturday: Ridgetop winds will remain light from the West. Alpine temperatures near -4 and freezing levels rising to 1600 m in the afternoon then falling to valley bottom overnight.

Avalanche Summary

Natural loose dry sluffing from steeper terrain, especially where the crust exists.

Snowpack Summary

Up to 40 cm of storm snow fell last weekend. Storm slabs exist on all aspects and elevations and are touchy, especially on slopes lee of the wind. Cornices have grown large on ridgelines and may act as a trigger on slopes below. Loose dry avalanches are likely, especially from steeper slopes and terrain features.Below 1900 m a crust has formed and may act as a sliding layer for the new snow. Below the crust the snowpack is moist. Mid and lower snowpack layers are generally well settled.

Problems

Storm Slabs

Storm slabs will continue to build with forecast snow, especially at upper elevations. They may be particularly touchy on slopes lee of the wind and are likely triggered by the weight of a person.

Avoid freshly wind loaded features.>Assess start zones carefully and use safe travel techniques.>The new snow may require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Dry

New low density storm snow may have a poor bond to current snow surfaces. Loose dry avalanches may occur, especially from steeper terrain features and slopes that have seen little wind effect.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Large cornices have formed with recent snow and wind. They may be weak and fail. Cornice fall in itself is dangerous, plus it could trigger slab avalanches on slopes below.

Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Mar 7th, 2013 2:00PM