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Avalanche Forecast

Mar 17th, 2015–Mar 18th, 2015
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
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

Winds have created a variable snowpack. Be alert to conditions that change with aspect and elevation.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Thursday

Weather Forecast

Generally light precipitation is expected on Wednesday, with the freezing level around 1700 m and winds light to moderate from the S to SW. Moderate snow is expected on Thursday and Friday (15-20 cm /day) above about 1600 m (rain at lower elevations). Winds are moderate to strong from the S to SW.

Avalanche Summary

A skier accidentally triggered a size 3 hard wind slab on Monday, which failed on the March crust/facet layer. Skiers also remotely triggered size 1.5-2.5 slabs, most on northerly aspects, some of which failed on the crust/facet layer. A natural and human-triggered cycle of wind slabs was reported on Sunday.

Snowpack Summary

Wind slabs (most recently formed with northerly winds, but previously lee to the S-SW) and wind-affected surfaces are the main theme at the snow surface. Cornices may also be fragile. Older, buried wind slabs may be hard to spot. A crust/facet persistent weak layer, buried anywhere from 10 to 60 cm down, has started to play up (see avalanche summary). Avalanche problems associated with this layer may linger for a while. A deeper crust (formed by heavy rain in February) is down around 70 cm. Below the deeper crust, the snowpack is reported to be generally well-settled and strong. Below treeline, the diminishing snowpack is trending isothermal (same temperature throughout).

Avalanche Problems

Wind Slabs

Recent outflow winds left touchy wind slabs on lee terrain features. Cornices may also be fragile.
Give cornices a wide berth when travelling on or below ridges.>Travel on ridgetops to avoid wind slabs on slopes below.>Avoid lee or cross loaded slopes at or above treeline.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

People have been remote-triggering persistent slabs. The buried crust/facet layer could produce surprisingly large avalanches.
Choose well supported terrain without convexities.>Avoid thin, rocky or sparsely-treed slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 5