Archived

Avalanche Forecast

Dec 6th, 2012–Dec 7th, 2012

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

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.

Some large avalanches have been reported running to valley bottom. Choose safe up-track locations and safe travel techniques.

Weather Forecast

Snowfall this morning will ease into light flurries with amounts in the 5-10cm range this AM. Drier conditions towards the weekend and cooler temperatures are expected.

Snowpack Summary

A 60cm storm slab is becoming increasingly cohesive due to recent strong winds. Nov28 layer which will be most reactive where it overlies a crust on S slopes or where surface hoar was buried in sheltered areas at treeline. The Nov 6 crust may become reactive with increasing load or may be triggered by another avalanche, creating a larger avalanche.

Avalanche Summary

Yesterday, distinct avalanche cycles occurred during periods of intense wind and snowfall. 1 size 3.5 and 2 size 2-2.5 natural avalanches were observed from paths adjacent to the highway. Notably some of the avalanches observed yesterday ran right to the valley bottom.

Confidence

Avalanche Problems

Wind Slabs

Strong S-SW winds have loaded lee slopes, triggering natural avalanches in steep terrain. Expect touchy loaded pockets, cornice development, and soft windslabs on lee slopes.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Extra caution needed around cornices with current conditions.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 2 - 4

Storm Slabs

We've received 100cm of snow on top of this layer at treeline which has settled into about 65cm of storm slab which will be most reactive where it buried surface hoar or sun-crust.

Be cautious of sluffing in steep terrain.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 2 - 3

Persistent Slabs

The Nov 6 crust complex has yet to wake up. While the likelihood of triggering is low, it will produce large avalanches. As the load on this layer increases, it may become reactive. Smaller avalanches may step down to this deeper layer.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4