Avalanche Forecast

Issued: Mar 5th, 2013 9:29AM

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

swerner, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Tonight and Wednesday: A low pressure system moves inland to the South of the border. Light-moderate of precipitation will begin this evening over the Southern ranges. Ridgetop winds light from the SE. Alpine temperatures near -4 and freezing levels 1800 m. Thursday: Mainly cool and dry with some clouds. Ridgetop winds light from the West. Alpine temperatures near -7 and freezing levels at 1300 m. Friday: The ridge will remain over the region with mainly dry, sunny conditions. Ridgetop winds light from the West. Alpine temperatures near -6 and freezing levels at 1600 m.

Avalanche Summary

Natural loose dry sluffing from steeper terrain. Explosive avalanche control initiated two size 2 slab avalanches from a North aspect around 1800 m.

Snowpack Summary

Up to 40 cm of storm snow fell last weekend. Storm slabs exist on all aspects and elevations and are touchy 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 with new snow accumulations. 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.>If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.>

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

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

Valid until: Mar 6th, 2013 2:00PM