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Avalanche Forecast

Mar 19th, 2015–Mar 20th, 2015
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
1: Low
The avalanche danger rating below treeline will be low
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
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.

New snow, strong winds and rising temperatures make a great recipe for avalanches. Add in a touchy weak layer buried in the upper snowpack and things may get a bit spicy.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Moderate to heavy precipitation is expected to continue until late Saturday. Anticipated amounts: by Friday morning – 20-35 cm; Friday – 15-25 cm; Saturday – 10-15 cm. The freezing level is the big question. It looks like it will hover around 1800 m, dropping towards 1200 m on Saturday. Winds are moderate to strong from the S-SW.

Avalanche Summary

A size 2.5 avalanche was observed from a distance on a north aspect at 2300 m. It is suspected to have been remotely triggered by a snowmobiler. 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 March crust/facet layer. A natural and human-triggered cycle of wind slabs was reported on Sunday. A round of storm slab activity is expected over the next few days in response to forecast snow and wind. Because of the buried persistent weak layer, avalanches might be bigger than expected for the amount of new snow.

Snowpack Summary

New snow will be landing on old hard wind slabs and wind-scoured surfaces. New storm slabs are expected to develop. Cornices may also be fragile. 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 with the potential for large and destructive avalanches. 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

Storm Slabs

New snow, wind and rising temperatures make a good recipe for avalanches. Leeward slopes will be most prime.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Persistent Slabs

In recent days, people have remotely triggered large persistent slab avalanches. New snow overloading this weak layer could cause surprisingly large avalanches.
Avoid convexities or areas with a thin or variable snowpack.>Pay attention to overhead hazards.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 5