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Avalanche Forecast

Dec 14th, 2011–Dec 15th, 2011
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
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
2: Moderate
The avalanche danger rating at treeline will be moderate
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Purcells.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Thursday: Expect the clouds to dissipate through the day, with a chance of flurries tapering into the evening. Winds should be light westerlies with temperatures reaching -6. Friday & Saturday: Clouds rebuild bringing intermittent flurries giving as much as 10cm each day. Winds in front of this disturbance will turn westerly. Expect daytime highs of -4.

Avalanche Summary

No new avalanches.

Snowpack Summary

5-10cm of new snow has fallen since the 10th of December. This overlies surface hoar, surface facets, old windslabs and sun crusts (on steep south through west aspects). Winds have been sporadic in this period, creating isolated new soft slabs in immediate lee locations. Moving forward, the avalanche danger will increase as the load increases (either by new snow or wind). Be locally aware of changes and if obvious signs of instability are present (cracking, whumphing, recent activity on adjacent slopes) or rapid loading is taking place (heavy snowfall or strong winds) then scale down your terrain choices accordingly. Snow depths are quite variable through the region with 130-150cm in the alpine. There is still concern for triggering the weak basal facets/depth hoar, as these layers have shown sudden collapse results in stability test in shallow areas.

Avalanche Problems

Wind Slabs

Old windslabs lurk in lee locations in the alpine. The trace of new snow may hide the older slabs and develop into new softslabs with the forecasted flurries and wind. For more info on incremental loading, check the forecaster blog.

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

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3

Persistent Slabs

The weak facetted layer near the ground may still be triggered in shallow snowpack areas with the common trigger points being convexities, rocks or clumps of small trees.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 5