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Archived

Avalanche Forecast

Mar 2nd, 2013–Mar 3rd, 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
4: High
The avalanche danger rating at treeline will be high
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.

Rapid loading has created very dangerous avalanche conditions. It will take a few days for the snowpack to adjust to the new load. Until then, natural and human triggered avalanches are likely.

Weather Forecast

The "pineapple express" will begin to weaken today, but we still expect up to 15cm of snow today, strong SW winds and mild temps with freezing levels hovering around Rogers Pass. A ridge of high pressure builds on Sunday. Cooling temps should start to tighten up the snowpack, the winds and precip will taper off, but the sun may trigger avalanches.

Snowpack Summary

35cm of heavy snow in the last 24hrs and a total of 60cm in 48hrs is settling with warm temps. This has rapidly loaded the Feb 12 surface hoar/crust layer down ~1m. This layer is most prevalent at and below treeline. In the alpine, S'ly winds are transporting snow rapidly loading slopes and forming new windslabs. It rained up to 1300m yesterday.

Avalanche Summary

Rapid loading by snow and moderate southerly winds triggered a widespread natural avalanche cycle yesterday. 35 size 2-2.5 and 20 size 3-3.5 natural avalanches were observed along the highway. In avalanche control yesterday, 97 rounds of artillery were fired with the majority triggering size 2-3.5 avalanches, and one size 4.

Confidence

Avalanche Problems

Storm Slabs

60cm of heavy storm snow is settling with mild temps. Rapid loading yesterday triggered widespread large avalanches. The snowpack needs time to adjust to the new load and will still be touchy to human triggering.
It is a good time to stay within the boundaries of a ski resort.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3

Persistent Slabs

A weak surface hoar layer is now down ~1m. This layer has been triggered by humans; remotely from 40m away, with propagations up to 150m wide. Rapid loading and other avalanches triggered this layer yesterday producing very large avalanches.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 4

Wind Slabs

Moderate to strong southerly winds continue to transport snow. This is loading lee slopes, overloading the snowpack and triggering large avalanches, as well as forming windslabs on exposed slopes. These areas will take even more time to stabilize.
Avoid all avalanche terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3