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Archived

Avalanche Forecast

Mar 16th, 2013–Mar 17th, 2013
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Saturday night: Light snow. Light W winds. Freezing level at the surface.Sunday: Light to moderate snow. Light NW winds with gusty N winds. Alpine temperature near -7.Monday: Light snow. Light W winds, gusting to strong NW winds. Alpine temperature near -6.Tuesday: Light snow. Light SW winds. Alpine temperature near -11.

Avalanche Summary

A widespread natural avalanche cycle was observed during the recent storm, including loose dry and soft slab avalanches at the beginning of the storm, and wet avalanches in areas where it warmed up. Skiers also triggered wind slabs on lee slopes. Most avalanches were in the size 1.5-3 range and failed within, or at the base of, the storm snow.

Snowpack Summary

The recent storm dropped anywhere from 40 cm to 1 m of snow at upper elevations, while rain soaked the snowpack below treeline. The storm snow was very reactive, creating big avalanches. The freezing level was between 1700 m and 2400 m during the storm, and lowered on Saturday, most likely forming a frozen crust in some areas. Strong NW through SW winds have redistributed snow into wind slabs and created cornices at alpine elevations. Below the storm snow is a layer of buried surface hoar and/or a crust. Deeper in the snowpack, a weak interface buried in mid-February is still on the radar. Although unlikely to be triggered, it remains possible with a very heavy load or from a thin-spot trigger point. A facet/crust layer sits at the base of the snowpack in some areas.As temperatures cool, wet slab/loose wet avalanche problems should improve, but persistent slab concerns at upper elevations may linger, especially on slopes which didn’t avalanche during the storm.

Avalanche Problems

Storm Slabs

New storm slabs may develop with forecast snow and wind, which will add to existing storm slab problems. Give the snowpack time to find its equilibrium before considering aggressive terrain.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be alert to conditions that change with elevation.>Be wary of slopes that did not previously avalanche - even on low angle terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 6

Cornices

Cornices are tender and can trigger slabs on slopes below. Give them a wide berth.
Avoid steep slopes below cornices.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4