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Archived

Avalanche Forecast

Feb 22nd, 2015–Feb 23rd, 2015
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
1: Low
The avalanche danger rating in the alpine will be low
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
1: Low
The avalanche danger rating in the alpine will be low
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Glacier.

Wind slabs have gained enough cohesion to be a real concern for human triggering.    Manage exposure to steep solar aspects when sun shines and temperatures rise.

Weather Forecast

A slight temperature inversion is at play this morning with cooler air in the valley bottoms.  A ridge of high pressure continues to block all precipitation. Expect mostly sun with cloudy periods, light NW winds, and freezing levels rising to 1200m. The high pressure system weakens Tuesday, allowing a weak low pressure system to move over the area.

Snowpack Summary

Below 1900m a light dusting of new snow sits on a bulletproof crust. Up to 2200m 15-20cm of light snow sits on the Feb 18 crust/ surface hoar layer. The Feb 14 crust is down 20-25 and is up to 10cm thick. Soft wind slabs on all aspects have formed in exposed areas at treeline and above. Persistent weak layers down 1-1.5m are stubborn to trigger.

Avalanche Summary

No new avalanches were observed yesterday in the highway corridor. A field team on Mt Fidelity observed cracking in pockets of soft wind slab at treeline. Reports of small skier controlled avalanches on wind loaded pockets near ridgeline.

Confidence

Avalanche Problems

Wind Slabs

Winds slabs have gained critical cohesion and can be triggered by human loads.  Wind slabs may propagate larger than expected on a buried crust up to 2200m. Fragile cornice growth at ridge line will continue to be touchy.
Be cautious as you transition into wind affected terrain.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

Persistent weak layers down ~1 to 1.5m will likely need a large load such as a cornice failure to be triggered. A light load, like you, may be able to trigger them from shallow areas. When triggered these layers may propagate widely.
Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 3 - 4