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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
3: Considerable
The avalanche danger rating below treeline will be considerable
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

Regions: Glacier.

While natural avalanche activity is slowing down, the snowpack is still adjusting to it's new load. Skier triggering remains likely.

Weather Forecast

Unsettled conditions are expected to continue. Light to moderate precip is expected today, possibly depositing up to 10cm of snow. Freezing levels will remain around 1300m, with moderate-strong SW winds. Overnight, temps should cool with freezing levels lowering to valley bottom. Light flurries and moderate W'ly winds are expected through Monday.

Snowpack Summary

Dense snow was rapidly deposited on a reactive layer down 55-65cm, which consists of a variety of surfaces including small surface hoar and crust. The storm snow is wet below 1650m and moist to 2000m. At treeline and above, sustained winds have further loaded slopes and formed windslabs. A surface hoar layer down 1.2m continues to be monitored.

Avalanche Summary

Natural avalanche activity tapered off yesterday, following this weeks widespread cycle. During the week, numerous avalanches were observed running to valley bottom with many in the size 3.5 range.  Cracking was reported yesterday when ski cutting steep, supported rolls. A slab avalanche 65cm deep was triggered by loading snow. The debris was 1.5m.

Confidence

Avalanche Problems

Storm Slabs

Last weeks warm and wet storm rapidly deposited 50-60cm of heavy, moist snow at treeline. This was deposited on low density snow sitting on a crust and or surface hoar and is bonding poorly. At lower elevations, rain saturated the upper snow.
Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 4

Persistent Slabs

It will likely take a large trigger, like a cornice fall or another avalanche to trigger the surface hoar/crust layer from February down 1-1.5m. If triggered, however, the resulting avalanche would be very large and destructive.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Choose regroup spots that are out of avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 3 - 4

Wind Slabs

Sustained S-SW winds have been forming windslabs on lee terrain above treeline. In these areas, deeper pockets of loaded snow will be more easily triggered.
Be cautious as you transition into wind affected terrain.Stay off recent wind loaded areas until the slope has had a chance to stabilize.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 3