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Archived

Avalanche Forecast

Mar 15th, 2013–Mar 16th, 2013
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

A strong storm over the last few days with heavy precipitation including snow and rain with strong winds has created dangerous avalanche conditions. Be cautious if you are traveling in the back-country. Avalanches are running to valley bottom.

Weather Forecast

The heavy precipitation overnight will backoff to light today, and the strong winds overnight should become light today and then rise back to moderate on Saturday. Overnight at Rogers Pass we recorded 1cm of snow and 28.5mm of rain. Light snowfall and cooling temperatures are forecast for the weekend.

Snowpack Summary

55cm of heavy, high density new snow now sits on top of the low density previous storm snow at treeline. The recent high winds have formed this snow into wind and storm slabs at treeline and in the alpine. Below 1700m there was a combination of rain and snow which did not refreeze overnight.

Avalanche Summary

A cycle of avalanche activity that began on Wednesday caused by rapid loading of the new snow by the very strong winds, and rising temperatures, continued yesterday. Numerous avalanches were observed yesterday running to valley bottom from artillery fire and natural triggers, with many in the size 3.5 range.

Confidence

Avalanche Problems

Storm Slabs

A storm that started on Wednesday has brought  40-60cm of high density new snow with strong winds and rising temperatures. This has formed avalanche conditions.
Choose conservative lines and watch for clues of instability.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 4

Persistent Slabs

The surface hoar/crust layer from February is most likely to be triggered by large triggers such as avalanches triggered in shallower layers in the snowpack and cornice falls which will result in large avalanches.
Sluffs may trigger deeper instabilities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 4