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Archived

Avalanche Forecast

Feb 21st, 2013–Feb 22nd, 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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

The weakness in the upper snowpack remains a concern for skier triggering with potentially wide propagations.  The incoming storm forecasted for tomorrow is expected to overload this tricky layer.  Cornices are growing larger with strong winds.

Weather Forecast

A ridge will remain over the region today, keeping things fairly dry.  Later today a frontal system will slide into the region bringing increased cloud and flurries.  Winds will be light to moderate from the W-SW.  On Friday a stronger front will push through, with forecasted snowfall amounts of 25-35 cm and strong westerly winds.

Snowpack Summary

Hard and Soft slabs overly a weak layer of surface hoar, buried 50-60cm. This surface hoar is wide spread, and is best preserved and reactive between 17-1900m, and is most reactive on solar aspects where it rests on a buried sun crust.

Avalanche Summary

Few natural avalanches have been observed in the backcountry.  Avalanche control yesterday produced a few avalanches to size 2.5.  While avalanche activity has tapered off lately, test results in profiles consistently produce easy fast shears (RB2 Whole Block) done 50 cm on the Feb. 12 surface hoar PWL.  This PWL can be found almost everywhere.

Confidence

Intensity of incoming weather systems is uncertain on Friday

Avalanche Problems

Persistent Slabs

A "persistent weak layer" (Feb 12 SH) is down 50-60 cm from the surface, and remains sporadically reactive to skier triggering.  Wide propagations are possible, especially on sunny aspects where it sits on a sun crust, between 17-1900m.
Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.Avoid runouts where triggering slopes from below is possible.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Wind Slabs

Wind slabs persist in lee loaded features near ridge crests and roll-overs.  These have the potential to step down to the Feb 12 PWL, creating larger avalanches in specific terrain features.
Assess start zones carefully and use safe travel techniques.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2